Answer:
Explanations:
Answer:
Explanations:
Scientists discovered a rock formation in the mountains that
contains some amount of Uranium-235. Upon further testing you
learn that the rock is composed of 25% Uranium-235. Knowing that
the rock is 1.426 billion years old, how long is the half-life of
Uranium-235?
The half-life of the Uranium-235, given that the rock is composed of 25% Uranium-235 is 713 million years
How do i determine the half-life?First, we shall calculate the number of half lives that has elapsed. This can be obtained as follow:
Original amount of Uranium-235 (N₀) = 100%Amount remaining of Uranium-235 (N) = 25%Number of half-lives (n) =?2ⁿ = N₀ / N
2ⁿ = 100 / 25
2ⁿ = 4
2ⁿ = 2²
n = 2
Finally, we shall determine the half-life of the Uranium-235. This can be obtained as follow:
Number of half-lives (n) = 2 Age of rock (t) = 1.426 billion years Half-life (t½) = ?n = t / t½
Cross multiply
n × t½ = t
Divide both sides by n
t½ = t / n
t½ = 1.426 / 2
t½ = 713 million years
From the calculations made above, we can conclude that the half-life is 713 million years
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Aluminum reacts with chlorine gas to form aluminum chloride. (a) If 35g of aluminum reacts with excess chlorine, how many grams of aluminum chloride will form. (b) How many grams of chlorine will react completely with 42.8 g of aluminum 2Al + 3Cl2 ==> 2AlCl3
Answer
(a) 172.848 grams
(b) 168.584 grams
Explanation
The balanced equation for the reaction of aluminum with chlorine gas is:
[tex]2Al+3Cl_2\rightarrow2AlCl_3[/tex](a) Mass of Al = 35 g
From the Periodic Table;
Molar mass of Al = 27 g/mol
Molar mass of AlCl₃ = 133.34 g/mol
From the balanced equation above; 2 moles Al produced 2 moles AlCl₃
So in grams, 2 mol x 27 g/mol = 54 g Al produced 2 mol x 133.34 g/mol = 266.68 g AlCl₃
Therefore, 35 g Al will form:
[tex]\frac{266.68\text{ g AlCl}_{3}\text{ }\times35\text{ g Al}}{54\text{ g Al}}=172.848\text{ g AlCl}_{3}[/tex]172.848 grams of aluminum chloride will be formed.
(b) Mass of Al = 42.8 g
Also from the Periodic Table; the molar mass of Cl₂ = 70.90 g/mol
From the equation above; 2 mol of Al requires 3 mol Cl₂.
In grams, 2 mol x 27 g/mol = 54 g Al requires 3 mol x 70.90 g/mol = 212.7 g Cl₂
Hence, 42.8 g Al will react with:
[tex]\frac{42.8\text{ g Al }\times212.7\text{ g Cl}_{2}}{54\text{ g Al}}=168.584\text{ g Cl}_{2}[/tex]168.584 grams of chlorine will react completely with 42.8 g of aluminum
Consider the balanced chemicalreaction below and determine thepercent yield for carbon dioxide if 4.50moles of propane yielded 7.64 moles ofcarbon dioxide.C3H8 +502 + 3CO2 + 4H2O-→
To solve this, we must know some terms:
% Yield = (Actual yield / Theoretical yield) x 100
Actual yield is already given = 7.64 moles
To obtain the theoretical yield, we use stoichiometry and proceed like this:
C3H8 + 5O2 => 3CO2 + 4H2O
1 mole C3H8 ------- 3 x 1 mole CO2
4.5 moles C3H8 ------ x
x = 13.5 moles
Therefore, our % yield:
% Yield = (7.64 moles/13.5 moles) x 100 = 57 % approximately
Answer: % yield = 57 %
A radioactive substance is found to register 5000 counts per second on a Geiger counter. Twenty-four hours later it registers 1250 counts per second. What is its half-life?
Answer
The half-life of the radioactive substance = 12 hours.
Explanation
Given that:
R₀ = 5000 counts/sec
R₁ = 1250 counts/sec
t = 24 hr
What to find:
The half-life of the radioactive substance.
Step-by-step solution:
The half-life of life of the radioactive substance can be calculated using the formula below:
[tex]\frac{0.693t}{T_{1\text{/}2}}=ln(\frac{R_0}{R_1})[/tex]Putting the values of the parameters into the formula, we have:
[tex]\begin{gathered} \frac{0.693\times24}{T_{1\text{/}2}}=ln(\frac{5000}{1250}) \\ \\ \frac{16.632}{T_{1\text{/}2}}=ln(4) \\ \\ \frac{16.632}{T_{1\text{/}2}}=1.3863 \\ \\ T_{1\text{/}2}=\frac{16.632}{1.3863} \\ \\ T_{1\text{/}2}=11.997\text{ }hr \\ \\ T_{1\text{/}2}\approx12\text{ }hr \end{gathered}[/tex]Thus, the half-life of the radioactive substance is 12 hours.
Write a balanced chemical reaction for each of the following double replacement reactions:
a. Hydrochloric acid reacts with sodium hydroxide.
b. Hydrochloric acid reacts with barium hydroxide.
c. Hydrochloric acid reacts with ammonium hydroxide
Balanced chemical reaction for each of the following double replacement reactions:
a) HCl + NaOH -----> NaCl + H₂O
b) 2HCl + Ba(OH)₂ ----> BaCl₂ + 2H₂O
c) 3HCl + Al(OH)₃ ----> AlCl₃ + 3H₂O
Balanced chemical reaction is when the number of atoms in the reactant sides are equal to the no. of atoms in product side.
a) Hydrochloric acid reacts with sodium hydroxide.
HCl + NaOH -----> NaCl + H₂O
b) Hydrochloric acid reacts with barium hydroxide.
2HCl + Ba(OH)₂ ----> BaCl₂ + 2H₂O
c) Hydrochloric acid reacts with ammonium hydroxide
3HCl + Al(OH)₃ ----> AlCl₃ + 3H₂O
Thus, Balanced chemical reaction for each of the following double replacement reactions:
a) HCl + NaOH -----> NaCl + H₂O
b) 2HCl + Ba(OH)₂ ----> BaCl₂ + 2H₂O
c) 3HCl + Al(OH)₃ ----> AlCl₃ + 3H₂O
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A reaction take place between an acid and 0.5 grams of powdered magnesium. Which statement is true?A. The powdered magnesium reacts faster because the activation energy has been lowered.B. The magnesium tracts reacts faster because It has a higher concentration of magnesium.C. The powdered magnesium react faster because it has a greater surface area.D. The magnesium react faster it will create a higher temperature once the reaction starts
Explanation:
The rate of a reaction is defined as the rate of disappearance of reactants in a reaction or the rate of conversion of appearance of products during a reaction.
The rate of a reaction depends on the concentration of the reactants, the temperature of the reaction, the nature of reactants, and the presence or absence of catalysts during the reaction.
The surface of reactants comes into play. Reactants with high surface areas react faster than reactants with fewer surface areas. Hence, powdery reactants react faster than solid reactants.
Answer: C. The powdered magnesium react faster because it has a greater surface area.
How many grams of CO are produced when 33.0 g of C reacts? Fe2O3(s)+3C(s)→2Fe(s)+3CO(g)
Answer
77.0 grams of CO are produced when 33.0 g of C reacts.
Explanation
Given:
Mass of C = 33.0 g
Equation: Fe₂O₃(s) + 3C(s) → 2Fe(s) + 3CO(g)
What to find;
The grams of CO that are produced when 33.0 g of C reacts.
Step-by-step solution:
Step 1: Convert 33.0 g of C to moles.
Using the formula for moles and the molar mass of C = 12.0 g/mol, the moles of C is
[tex]\begin{gathered} Moles=\frac{Mass}{Molar\text{ }mass} \\ \\ Moles\text{ }of\text{ }C=\frac{33.0\text{ }g}{12.0\text{ }g\text{/}mol}=2.75\text{ }mol \end{gathered}[/tex]Step 2: Determine the moles of CO produced.
Using the mole ratio of C and CO from the balance equation and the moles of C in step 1; the moles of CO produced is calculated as follows:
[tex]\begin{gathered} 3\text{ }mol\text{ }C=3\text{ }mol\text{ }CO \\ \\ 2.75\text{ }mol\text{ }C=x \\ \\ x=\frac{2.75\text{ }mol\text{ }C}{3\text{ }mol\text{ }C}\times3\text{ }mol\text{ }CO \\ \\ x=2.75\text{ }mol\text{ }CO \end{gathered}[/tex]Step 3: Convert the moles of CO produced to mass in grams.
The moles of CO produced in step above can be converted to mass in grams as shown below
[tex]\begin{gathered} Mass=Moles\times Molar\text{ }mass \\ \\ Molar\text{ }mass\text{ }of\text{ }CO=12.0+16.0=28.0\text{ }g\text{ /}mol \\ \\ Mass\text{ }of\text{ }CO\text{ }produced=2.75\text{ }mol\times28.0\text{ }g\text{/}mol \\ \\ Mass\text{ }of\text{ }CO\text{ }produced=77.0\text{ }g \end{gathered}[/tex]Hence, 77.0 grams of CO are produced when 33.0 g of C reacts.
Balance each of these reactions and indicate the type of reaction each equation represents: a) NH3 → N2 + H2 b) Ba(C2H3O2)2 + Na3PO4 → Ba3(PO4)2 + NaC2H3O2 c) Zn + HCl → ZnCl2 + H2 d) Hg + O2 → HgO
Answer:
Explanation:
Here, we want to balance the chemical equation and state the type of chemical reaction
In balancing the chemical equation, we have to ensure that the number of atoms we have on the left hand side is same as what we have on the right hand side
We have this as:
[tex]3Ba(C_2H_3O_2)_2+2Na_3PO_4\text{ }\rightarrow Ba_3(PO_4)_2+6NaC_2H_3O_2[/tex]To get the type of reaction, we can see that there is an exchange of ionic groups between the individual metallic ions
This type of reaction is called a double displacement reaction
25.0 mL of a solution with concentration 0.30 M is diluted to a final volume of 150. mL. What is the final concentration?
Answer: the concentration of the solution after the dllution is 0.050 M
Explanation:
The question requires us to determine the concentration of a solution after a dilution process.
The following information was provided by the question:
Concentration of initial solution = C1 = 0.30 M
Volume taken from initial solution = V1 = 25.0 mL
Volume of final solution = V2 = 150 mL
When a solution is diluted, the number of moles of the substance remains the same. Thus, we can say that:
[tex]n_1=n_2[/tex]where (1) is the solution before dilution and (2) refers to the solution after dilution.
The number of moles of a substance can be obtained from the definition of molarity (or molar concentration), where the number of moles is divided by the volume of the solution:
[tex]molarity=\frac{number\text{ of moles}}{volume}\rightarrow number\text{ of moles = molarity}\times volume\rightarrow n=C\times V[/tex]Thus, we can write that for a dillution:
[tex]n_1=n_2\rightarrow C_1\times V_1=C_2\times V_2[/tex]From the expression above we can determine the concentration of the final solution. Applying the values provided by the question to the expression above, we'll have:
[tex]\begin{gathered} \begin{equation*} C_1\times V_1=C_2\times V_2 \end{equation*} \\ \\ (0.30M)\times(25.0mL)=C_2\times(150mL) \\ \\ C_2=\frac{(0.30M)\times(25.0mL)}{(150mL)}=0.050M \end{gathered}[/tex]Therefore, the concentration of the solution after the dilution is 0.050 M.
Which type of radiation would you consider ionizing radiation?MicrowavesVisible lightSound wavesGamma rays
Ionization radiation is a type of energy with such a high value that it is capable of removing electrons from atoms and converting them into ions. This type of energy is extremely dangerous. The types of energy that fall into this category are X-rays and gamma rays.
So, the answer will be Gamma rays
How much heat is released when 245 g of steam cools from 106.0°C to -4.5°C
ANSWER
The amount of heat released is -54, 957.175J
EXPLANATION
Given that;
[tex]\begin{gathered} \text{ The mass of the steam is 245g} \\ \text{ The final temperature of the steam is -4.5}\degree C \\ \text{ The initial temperature of the steam is 106.0}\degree C \end{gathered}[/tex]To find the amount of energy released, then apply the below formula
[tex]\text{ q = mc \lparen}\theta2\text{ - }\theta1)[/tex]Recall, that the specific heat capacity of steam (c) is 2.03 J/g degrees Celcius
[tex]\begin{gathered} \text{ q = 245 }\times\text{ 2.03 \lparen-4.5 - 106\rparen} \\ \text{ q = 245 }\times\text{ 2.03 \lparen -110.5\rparen} \\ \text{ q = -54,957.175J} \end{gathered}[/tex]Therefore, the amount of heat released is -54, 957.175J
Many people use a microwave oven to cook their food. When it is turned on, what type of energy transfer is taking place?A. Electrical to chemicalB. Nuclear to heatC. Electromagnetic to soundD. Electrical to electromagnetic
Explanation:
The microwave receives, from a transformer (energy source), a fixed voltage and generates, through the vibration of electrons in its resonant cavities, electromagnetic waves inside the device.
Answer: D. Electrical to electromagnetic
what are the limiting and excess reactants when 26.62 moles of FeS2 react with 59.44 moles of O2
Step 1
The reaction must be completed and balanced as follows:
4 FeS2 + 11 O2 => 2 Fe2O3 + 8 SO2
-------------------------
Step 2
Information provided:
26.62 moles of FeS2
59.44 moles of O2
-------------------------
Step 3
The limiting and the excess reactant
Procedure: by stoichiometry,
4 FeS2 + 11 O2 => 2 Fe2O3 + 8 SO2
4 moles FeS2 ------------ 11 moles O2
26.62 moles FeS2 ------------ X
X = 26.62 moles FeS2 x 11 moles O2/4 moles FeS2
X = 73.20 moles
For 26.62 moles of FeS2, 73.20 moles of O2 are needed, but there are only 59.44 moles so the limiting reactant is O2, and the excess reactant is FeS2.
Answer:
The limiting reactant = O2
The excess reactant = FeS2
How many moles of magnesium is 5.01 x 10^22 atoms of magnesium?
The question requires us to calculate the number of moles that corresponds to 5.01 x 10^22 atoms of magnesium.
To solve this question, we'll need to use the Avogadro constant. This number, defined as 6.02 x 10^23, relates the number of constituent particles (molecules, atoms or ions, for example) in a sample with the amount of substance in that sample. We can use it by saying that 1 mol of a substance corresponds to 6.02 x 10^23 constituent particles of this substance.
Then, using the information above, we can calculate the number of moles in 5.01 x 10^22 atoms of magnesium (Mg):
6.02 x 10^23 atoms of Mg --------------- 1 mol of Mg
5.01 x 10^22 atoms of Mg ---------------- x
Solving for x, we'll have:
[tex]x=\frac{(5.01\times10^{22}\text{ atoms of Mg)}\times(1\text{ mol of Mg)}}{(6.02\times10^{23}\text{ atoms of Mg)}}=0.0832\text{ mol of Mg}[/tex]Therefore, 5.01 x 10^22 atoms of magnesium corresponds to 0.0832 mol of this element.
Please help
For this assignment, you will create a public service
announcement, or a PSA, describing the environmental
and economical impact of the end-products of
chemical reactions of those that may result in the
greenhouse effect or ozone depletion.
Items you must include or address:
• describe the chemical reaction
occurring using a
chemical equation and identifying the reactants
and products.
• demonstrate how mass/matter is conserved
during this chemical reaction.
• describe the energy changes that accompany this
chemical reaction.
• describe how the end-products affect the
environment.
• describe the economical impact.
provide ways for anyone to help reduce the
environmental impacts.
I need to be a letter to your senator
The assignment about the Public Service Announcement (PSA) describing the environmental impacts due to ozone depletion and the greenhouse effect is given below.
Since we live in a modern industrialized world, we need to get exposed to lots of chemicals and pollutants. With modernization people began to use Air conditioners, Refrigerants, and other household appliances for a sophisticated lifestyle without knowing the harmful effects it causes on the environment.
The use of Refrigerators and Air Conditioners contains Freons which are used as aerosol propellants. These freons release CFCs which are called as Chloro-Fluro-Carbons which are the main element responsible for damaging the environment by causing both global warming and Ozone depletion.
The Chlorine atom that is released from the CFCs breaks the bond of the Ozone. The reaction is elucidated below:
ClO + O -------> Cl + O₂
This breaks the bond of Ozone creating Ozone depletion and eventually leading to Global Warming.
Similar to Ozone depletion, another main environmental problem is the greenhouse effect which is occurring mainly due to the release of harmful gases from automobiles, and industries such as CO₂, SO₂, etc... These gases absorb and trap the solar heat from the Infrared region and creates a greenhouse effect. These gases are called greenhouse gases.
This greenhouse effect, ozone depletion eventually leads to an increase in global temperature and results in the rising of sea levels by melting the glaciers and icebergs. The climatic pattern is adversely affected. This would affect agriculture, as well as the health of humans as harmful UV rays that enter the earth due to ozone depletion, will lead to skin diseases, cancer, and so on.
By adversely affecting the agriculture and health of the world, there would be a drop in the entire economy as our country is dependent mainly on agriculture for the nation's economy.
The effects of these could be minimized by using public transport, planting trees, using refrigerators and air conditioners free from freons, and proper treatment of the wastes eliminated from industries must be ensured.
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How many liters of a 0.75 M solution can be made with 75 grams of lead (ll) oxide?
Step 1
Molarity is defined as:
Molarity (M or mol/L) = Moles of lead (II) oxide/Volume of solution (L)
Molarity = mass of lead (II) oxide/molar mass of lead (II) oxide x volume (L) (1)
-------------------------
Step 2
The molar mass of PbO = 223 g/mol
PbO = lead (ll) oxide
------------------------
Step 3
Data provided:
Molarity = 0.75 M
Mass of PbO = 75 g
------------------------
Step 4
Procedure:
The volume of the solution is cleared from (1):
Volume (L) = mass PbO/(molar mass PbO x Molarity)
Volume (L) = 75 g/(223 g/mol x 0.75 mol/L) = 0.45 L approx.
Answer: Volume = 0.45 L
Draw the Lewis structure of hcp. Which of the following statement is incorrect?
Answer:
[tex]H-C\equiv P^{\cdot\cdot_{}}_{}[/tex]
Explanation:
Here, we want to draw the lewis structure of HCP
We have the participating compound as, hydrogen with 1 valence electron, carbon with 4 valence electrons and phosphorus with 5 valence electrons
We would have three bonds between the carbon and the phosphorus, then we have a bond between the hydrogen and the carbon
That would leave a pair of non-bonding electrons on the phosphorus
We have the diagram as follows:
[tex]H-C\equiv P^{\cdot\cdot_{}}_{}[/tex]Now, let us look at the options:
option A is wrong as the bond in a triple bond
option B is correct, there are no lone pairs on C
option C is correct as the C-H bond is a single bond
option D is correct as there is a pair of electron on the phosphorus atom
A certain copper ore contains 3.24% of Cu2S by mass. In 1991, a single open-air smelt furnace heated 30000 tons of this ore. Compute the mass of copper metal obtained by this process. Enter in tons.
The mass of the copper that is obtained is 97.2 tons.
What is combustion?We can define the term combustion as the procedure by which a substance can be burnt in oxygen. We can also be able to refer to the process as roasting the object in the air. It is an oxidation reaction.
Having said all all of these, the reaction equation can be written as;
[tex]Cu_{2} S + O_{2} ------ > 2Cu + SO_{2}[/tex]
We know that the percent of the copper that it contains can now be used when we are trying to compute the mass of the copper that can be obtained from the process as we are going to have in the question that is at hand here to solve.
We are now going to proceed to see the mass of the copper that can be produced from the 300 tons of the copper I sulfide ore given.
Thus;
The mass of copper that can be obtained is;
3.24/100 * 3000 tons
= 97.2 tons
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Calculate the AHrxn from the AH of formation for the following reaction. C2H4(g) + 302(g) 2C02(g) + 2H20(1). Formation AH values for C2H4(g) = 52.30 kJ/mol, for 02(g) = 0 kJ/mol, for CO2(g) = -393.5 kJ/mol and for H20(1) =-285.8kJ/mol.A. -1305kJB. 1350kJC. 1411kJD. -1411kJ
Answer
A. -1305 kJ
Explanation
Given:
Equation: C2H4(g) + 302(g) ---- > 2C02(g) + 2H20(l).
Formation ΔH values:
for C2H4(g) = 52.30 kJ/mol,
for 02(g) = 0 kJ/mol,
for CO2(g) = -393.5 kJ/mol, and
for H20(1) = -285.8kJ/mol.
What to find:
The ΔHrxn from the ΔH of formation for the given reaction.
Step-by-step solution:
ΔHrxn = (Sum of ΔH formation for the product) - (Sum of ΔH formation for the reactants).
ΔHrxn = (ΔH for 2CO2(g) + ΔH for 2H2O(l)) + (ΔH for C2H4(g) + ΔH for 3O2(g))
ΔHrxn = [(2 x -393.5) + (2 x -285.8)] + [52.30 + (3 x 0)]
ΔHrxn =(-787.0 - 571.6) + (52.30 + 0)
ΔHrxn = -1358.6 + 52.30
ΔHrxn = -1306.3 kJ
so the closest answer is A. -1305 kJ
Predict the nature of the indicated
covalent bond.
H-C=N:
polar
non-polar
Answer:
I would say Polar
Explanation:
If you add 8 g of salicylic acid to 84 g of an ointment base, what is the final concentration (w/w) of the product? Round to the nearest hundredths (w/w).Question 3 options:Answer will be in % nothing else! ACTIVE INGREDIENT will always be your numerator.NUMERATOR (ACTIVE INGREDIENT)--------------------------------DENOMINATOR (TOTAL) Numerator means the top part of your fractionThe (w/w) is telling you to divideSTEPS: Add 8 + 84 this will be your denominator totalthen multiply by 100 to add the % sign in #----- Divide = then multiply by 100 for the percent sign. What is your answer?#FINISH THE MATH FOR THE CORRECT ANSWER
Answer
Concentration = (8/92)*100 = 8.7%
Explanation
Given:
mass of salicylic acid (active ingredient) = 8 g
mass of an ointment base = 84 g
Required: concentration (w/w) of the product?
Solution:
Total mass of the mixture = 8 + 84 = 92 g
Concentration = (8/92)*100 = 8.7%
Write down a specific step by step procedure of the titration process which the goal is to determine the unknown concentration of a basic solution.
Explanation:
Titration is a technique used to determine the amount of matter in a sample using a solution of known concentration. In other words, titration is a quantitative chemical analysis. In this process, the sample has its concentration determined through a chemical reaction when it is mixed with another substance. The use of pH indicators in this process is useful to determine the endpoint of the titration, indicating that the entire sample has reacted. Titration is used to accurately determine the amount of a substance, confirm that the concentration described on the label is true or that the amount of a chemical compound is indicated on the package.
Sample weighing: With the solid sample on a watch glass, weigh it on the balance.
Sample dissolution: The sample is transferred to an Erlenmeyer flask with water, where dissolution takes place.
Problem solution: The solution is transferred to a volumetric flask and the volume is made up with water, creating the problem solution.
Aliquot transfer: Remove an aliquot of the problem solution with the aid of a pipette and transfer it to an Erlenmeyer flask.
Titration: To the Erlenmeyer flask, the problem solution (titrated) is added and the solution of known concentration (titrant) is inserted into the burette.
An acid-base indicator is also added to the titrator to indicate when the titration should be stopped due to the color change. The color change indicates the end point or turning point of the titration.
After that, when the color change persists, the volume of titrant used is verified and stoichiometric calculations will help us to discover the concentration of the titrated solution.
Answer:
Step 1 - Sample weighing: With the solid sample on a watch glass, weigh it on the balance.
Step 2 - Sample dissolution: The sample is transferred to an Erlenmeyer flask with water, where dissolution takes place.
Step 3 - Problem solution: The solution is transferred to a volumetric flask and the volume is made up with water, creating the problem solution.
Step 4 - Aliquot transfer: Remove an aliquot of the problem solution with the aid of a pipette and transfer it to an Erlenmeyer flask.
Step 5 - Titration: To the Erlenmeyer flask, the problem solution (titrated - basic solution) is added and the solution of known concentration (titrant - acidic solution) is inserted into the burette.
Step 6 - An acid-base indicator is also added to the titrator to indicate when the titration should be stopped due to the color change. The color change indicates the endpoint or turning point of the titration.
Step 7 - After that, when the color change persists, the volume of titrant used is verified and stoichiometric calculations will help us to discover the concentration of the titrated solution.
Electrons in atoms exist in particular energy levels. A _______ must be emitted or absorbed to move between energy levels.Question 19 options:A) photonB) electronC) particleD) quantum
Answer: We can complete the sentence as:
"Electrons in atoms exist in particular energy levels. A photon must be emitted or absorbed to move between energy levels" (letter A).
Explanation:
The question requires us to choose the best option to complete the sentence: "A ________________ must be emitted or absorbed to move between energy levels".
Energy levels are fixed distances from the nucleus of an atom where electrons can be found. Energy levels can be compared to stairs in a staircase: we can stand on a step, on the previous step or the next step, but never between them; this is what happens to electrons, as they can occupy one energy level or another but not the space between energy levels.
To move from one energy level to another, an electron must absorb energy (to move to a higher level) or emit energy (to move to a lower level). The energy difference between a lower starting level and a higher ending level must correspond to the energy of a photon of light absorbed in order to make the transition between energy levels possible. Additionally, electrons are usually unstable at excited states (when at a higher energy level that it was initially), and the electron quickly returns to the lower energy level emitting the excess of energy in the form of light (as a photon of light).
Therefore, considering the information above, we can complete the sentence as:
"Electrons in atoms exist in particular energy levels. A photon must be emitted or absorbed to move between energy levels" (letter A).
Use the balanced equation to solve the problem.Na₂CO3 +CaCl2 → 2NaCl + CaCO3115g of CaCl₂ react.How many moles of NaCl are made?mol
2.0724moles
Explanations:Given the balanced chemical reaction between Na2CO3 and CaCl2 expressed as:
[tex]Na_2CO_3+CaCl_2\rightarrow2NaCl+CaCO_3[/tex]Given the following parameters
Mass of CaCl₂ = 115g
Determine the moles of CaCl₂
[tex]\begin{gathered} moles\text{ of CaCl}_2=\frac{mass}{molar\text{ mass}} \\ moles\text{ of CaCl}_2=\frac{115}{110.98} \\ moles\text{ of CaCl}_2=1.0362moles \end{gathered}[/tex]According to stochiometry, 1 mole of CaCl2 prodcues 2 moles of NaCl. The moles of NaCl requred is given as:
[tex]\begin{gathered} moles\text{ of NaCl}=2\times1.0362 \\ moles\text{ of NaCl}=2.0724moles \end{gathered}[/tex]Therefore moles of NaCl made is 2.0724moles
6.50×104 +8.70×105
[?]
? ]×10¹ ?
Answer:
9.35 × 10⁵
Explanation:
6.50x10⁴=6500
8.70×10⁵=870000
65000+ 870000= 935000=9.35 ×10 ⁵
9. A possible variant of gold has a mass of 192. Is this variant an isot
many neutrons does it have?
a. Yes; 79
b. No; 192
c. Yes; 113
d. Yes, 118
A possible gold variant has a mass of 192. Yes, it has 79 neutrons in this variant.
What is meant by variant?A variant is an additional version of something. Chimps, apes, and gorillas are all members of the primate family. Words frequently have variant spellings, which differ from region to region or country to country. The British and American colors are variations. A variant is an alternate spelling or form of an entry word. Variants follow the entry word in boldface and are preceded by or or also. The label or indicates that the variant is as common as, or nearly so, as the entry word. A variation is something that differs from a norm or standard, whereas a variant differs from other things in its own class that is, it does not necessarily differ from a norm or standard.The neutron is a subatomic particle with the symbol n or n0 that has a neutral charge and a slightly larger mass than a proton. Atomic nuclei are made up of protons and neutrons.To learn more about neutrons, refer to:
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70.0 mL of water was added to 100.0 mL of 0.250 M CaCl₂ solution. Assuming the volumes are additive, what is the CaCl₂ concentration in the diluted solution?
70.0 mL of water was added to 100.0 mL of 0.250 M CaCl₂ solution. Assuming the volumes are additive, The CaCl₂ concentration in the diluted solution is 0.147 M.
given that :
volume V1 = 100 mL
volume V2 = 100 + 70 = 170 mL
Molarity M1 = 0.250 M
Molarity M2 = ?
using dilution equation we get :
M1 V1 = M2 V2
M2 = ( M1 V1) / V2
M2 = ( 0.250 × 100 ) / 170
M2 = 0.147 M
Therefore , the dilution solution will have 0.147 M
Thus, 70.0 mL of water was added to 100.0 mL of 0.250 M CaCl₂ solution. Assuming the volumes are additive, what is the CaCl₂ concentration in the diluted solution is 0.147 M.
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I believe the incorrect statement is dissolution of oxygen in water is due to dipole- induced dipole interaction.
For this question we have 4 options and relates a few chemical concepts, let's analyze each option and reach a final conclusion:
A. Since in a geometric 3-D point of view, neopentane is more closely together in its bondings, the boiling point will be lower in it, and n-pentane has more surface to be heated, therefore the boiling and melting point will be higher, as it is proven experimentally, n-pentane = 36.1°C, neopentane = 9.5°C. Correct
B. If we have O2 being thrown in water, the covalent bonding between these two atoms is very nonpolar and weak, the weak Van der Waals force, also known as temporary dipole-induced dipole interactions. Correct
C. Dipole moment has a lot to do with the strength of a bond, greater the dipole moment, the stronger the bond will be, and if we have a strong bond, more energy will be required to break, therefore higher the boiling and melting point will be for these compounds, therefore this one is Incorrect
D. Yes, in DNA the main type of intermolecular force is Hydrogen bonding
Which phase change is endothermic?
A) H₂O(t)→ H₂O(g)
B) I2(g) → I2(s)
C) Hg(t)→ Hg(s)
D) H₂S(g) → H₂S(t)
How much heat in kJ is released when 0.677 mol NaOH(soln) is dissolved in water? (ΔH(soln) = –44.5 kJ/mol for NaOH)NaOH(s) rightwards arrow Na+(aq) + OH–(aq) + 44.5 kJ/mol
Explanation:
The dissolution reaction of NaOH is:
NaOH (s) -----> Na⁺ (aq) + OH⁻ (aq) + 44.5 kJ/mol
ΔH(soln) = –44.5 kJ/mol
This reaction is exothermic, because the ΔH is negative. That's why the 44.5 kJ/mol appears in the products side, because heat is being released.
From the ΔH of solution we know that 1 mol of NaOH will realease 44.5 kJ when it dissolves. We have to find the heat released by 0.677 mol of NaOH.
Heat released = 0.677 moles * (-44.5 kJ/mol)
Heat released = - 30.1 kJ
Answer: -30.1 kJ is released when 0.677 mol of NaOH is dissolved.