How many significant figures (SF) are in each of the following measured quantities? Drag the appropriate measurement to the respectable bins

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.

Answer:

9.35 × 10⁵

Explanation:

6.50x10⁴=6500

8.70×10⁵=870000

65000+ 870000= 935000=9.35 ×10 ⁵

A possible gold variant has a mass of 192. Yes, it has 79 neutrons in this variant.

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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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The half-life of the Uranium-235, given that the rock is composed of 25% Uranium-235 is 713 million years

First, we shall calculate the number of half lives that has elapsed. This can be obtained as follow:

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:

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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Answer:

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:

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

2.0724moles

Given the balanced chemical reaction between Na2CO3 and CaCl2 expressed as:

Given the following parameters

Mass of CaCl₂ = 115g

Determine the moles of CaCl₂

According to stochiometry, 1 mole of CaCl2 prodcues 2 moles of NaCl. The moles of NaCl requred is given as:

Therefore moles of NaCl made is 2.0724moles

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:

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

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).

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

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:

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

Hence, 77.0 grams of CO are produced when 33.0 g of C reacts.

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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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 %

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

According to the given statement Mass of one atom of gold in grams is 196.78 g.

A chemical element is uniquely defined by its atoms, that are small bits of substance. An atom is made up of a core nucleus one and or more negatively charged electrons that orbit it. The positively charged, relatively hefty protons and neutrons that make it up the nucleus may be present.

Up until the 1800s, this idea of tiny, indivisible pieces of matter remained. The contemporary atomic idea was really started by the eminent chemist John Dalton (1766–1844). But his atom was like a rock-solid ball.

Molar mass is the weight in grams of one mole of an atom.

1 mole = 6.022×10²³ atoms

Molar mass of Gold (Au)

= mass of an atom × number of atoms

=3.207×10-²²×6.022×10²³

=196.78g.

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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.

Answer:

I would say Polar

Explanation:

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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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:

Therefore, 5.01 x 10^22 atoms of magnesium corresponds to 0.0832 mol of this element.

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%

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

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

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.

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:

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:

Thus, we can write that for a dillution:

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:

Therefore, the concentration of the solution after the dilution is 0.050 M.

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:

Putting the values of the parameters into the formula, we have:

Thus, the half-life of the radioactive substance is 12 hours.

Kinetic energy refers to the work required to accelerate a body from an initial state of rest to infinite speed. So kinetic energy is related to the motion and speed of a body.

So the answer will be C. motion

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

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

Answer

(a) 172.848 grams

(b) 168.584 grams

Explanation

The balanced equation for the reaction of aluminum with chlorine gas is:

(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:

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:

168.584 grams of chlorine will react completely with 42.8 g of aluminum