Balance the chemical equation below using the smallest possible whole number stoichiometric coefficients.
[] → CH3,CH3,(g) +O2,(g) → CO2,(g) + H2O(g)

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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Ne is a noble gas, O is a non metal and Br is an halogen.

K is a metal that belongs to the same group as Na, it means that they have similar chemical properties.

It means that the answer is K.

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 ionic compound is made of two ions, one with positive charge and the other one with a negative charge.

The ion with positive charge is known as cation and the one with negative charge is known a anion.

It means that the correct answer is A. A positive cation and a negative anion.

Answer

0.0779 g SO₃

Procedure

To solve this question, you will need to use the Avogadro's number equivalent to 6.02214 x 10^23 molecules/ mol, and then the molecular weight in grams per mole for the SO₃.

ANSWER

The amount of heat released is -54, 957.175J

EXPLANATION

Given that;

To find the amount of energy released, then apply the below formula

Recall, that the specific heat capacity of steam (c) is 2.03 J/g degrees Celcius

Therefore, the amount of heat released is -54, 957.175J

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.

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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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

Explanation:

First, let's write the balanced equation of formation of MgCl2 from Mg and Cl2:

Mg + Cl2 → MgCl2

Now let's transform 10.0g of Mg into moles, using the following formula: moles = mass/molar mass

molar mass of Mg = 24.3 g/mol

moles = 10/24.3

moles = 0.412 moles

Now we use the equation ratio between Mg and MgCl2 to find the quantity of MgCl2 in moles.

1 mole of Mg produces 1 mole of MgCl2.

So 0.412 moles of Mg produces 0.412 moles of MgCl2.

Now we transform 0.412 moles of MgCl2 into mass using the following formula: mass = moles x molar mass

Molar mass of MgCl2: 24.3 + (2*35.45) = 95.21 g/mol

Mass = 0.412 * 95.21

Mass = 39.2 g

Answer: The theoretical yield of MgCl2 is 39.2 g.

Answer:

I would say Polar

Explanation:

1. Synthesis reaction : there is only 1 product formed from 2 or more reactant

E.g:

2. Decomposition : reaction that occurs in presence of UV light and only 1 reactant that decomposes into 2 or more products.

E.g:

3. Single displacement : reaction that occurs when 1 reactant displaces other reactant from its compound:

E.g:

4. Double displacement : reaction that occurs when both reactant displaces each other.

E.g :

Hydrogen bonding is formed when the partial negative charge at one end of a water molecule is attracted to the partial positive charge of another water molecule

Thus, when the partial negative charge at one end of a water molecule is attracted to the partial positive charge of another water molecule, hydrogen bonding is formed.

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If you only have the percent composition of each element in a give compound, you can't determine yet the empirical formular for the compound. The problem is, the percent composition only gives relative numbers for each element. What can be determined is the empirical stochiometry of one element relative to the others.

For example, supose you have a compound with element X and Y, with the percent composition you can determine how much X you have relative to how much Y you have. Say you determine that for each 2 X you have 3 Y, the formula can be X₂Y₃ but it can also be X₄Y₆ or even othre possibilities.

To determine the empirical formula you need to know how many of one of the elements you have in each compound. A common way of getting the empirical formula is to use the percent composition and, in addition, the molar mass of the compound, which will make it possible to get the empirical formula from the relative ratios of each element you have.

Kinect-molecular theory hypothesis:

- The formation of a gas occurs by a large number of molecules;

- Gas molecules have a negligible dimension, which means that the volume occupied by them is very small, almost insignificant;

- These gases move in a discontinuous and random way, thus occupying the entire volume of the container where they are found, having a rectilinear and uniformly varied movement;

- They are independent, they only interact with each other when a collision occurs;

- Collisions between molecules and molecules and between molecules and container walls are elastic collisions, which cause the kinetic energy of the molecules to remain constant.

Having seen these statements, the answers can only be:

The warmer a glass of water, the faster a drop of ink will spread through the water.

The colder a room is, the longer it would take to smell a spray of perfume from the other side of the room.

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).

The decay of this radioactive unknown compound is a first-order process.

We can express the time dependence of its mass m using a first-order integrated rate law, where k is the rate constant:

mt = mass at time t

m0 = initial mass

t = time

-----------------------------------------------------------------------------------------------------

Procedure:

1) We need to find "k":

From the first-order rate law we clear k,

----------------------------------------------------------------------------------------------

2) We find the half-life from the value of k we have just calculated:

-----------------------------------------------------------------------------------------------

3) The number of half-lives of the unknown sample is:

Number of Half-lives = 47 days / 15.7 days = 3 (approx.)

Answer: Number of half-lives = 3

The mass of the copper that is obtained is 97.2 tons.

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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Structural formulas are ways atoms and elements are arranged in a molecule. The structural formula of pentane, pentene, and pentyne are as shown below;

Pentane - C5H12

Pentene - C5H10

Pentyne - C5H8

e) Pentane is an alkane compound with a general formula CnH2n+2. The chemical formula of pentane is C5H12. There are only single bonds between the C-H atoms in the molecule.

Pentene is an alkene compound with a general formula of CnH2n. The chemical formula of pentene is C5H10. There is a double bond present between the C=H atoms. This double bond shows that the compound is an alkene.

Pentyne is an alkyne compound with a general formula of CnH2n-2. The chemical formula of pentene is C5H8. There is a triple bond present between the Carbon Hydrogen atoms. This presence of a triple bond shows that the molecule is an alkyne compound.

Answer:

Atoms

Explanation:

Answer:

atoms

Explanation:

its right, trust

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

Avogadro's number states that:

1 mol of Cu = 63.54 g of Cu = 6.02x10^23 atoms of Cu

Now, we proceed like this:

1 kg = 1000 g ===> 187 kg = 187,000 g

63.54 g Cu -------- 6.02x10^23 atoms of Cu

187,000 g Cu -------- X

X = 1.77x10^27 atoms Cu

Answer: 1.77x10^27 atoms Cu

answer and explanation

Radioactivity is the emission of ionizing radiation from nuclear decay. there are three types of radioactive decay.

alpha decay

in alpha decay an alpha particle is released. In the parent atom, the atomic number decreases by 2 and the atomic mass decreases by 4

beta decay

in beta decay a beta particle is released, the atomic number is unchanged and the atomic mass increases by 1

gamma decay

in gamma decay, energy is released as gamma rays from an excited nuclear state. the atomic mass and atomic number remain unchanged.

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:

C

Explanation:

Because the suspect touched something at the crime scene and thus he's fingerprint are matching

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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Step 1

The reaction must be completed and balanced:

4NH3 (g) + 9O2 (g) => 4NO3 + 6H2O (g)

Reactants: NH3 and O2

Products: NO3 and H2O

--------------------

Step 2

Information provided:

STP conditions, therefore:

1 mole of gas (NH3 in this case) = 22.4 L (volume)

5.3 g of O2

Liters => L

Grams => g

---------

Information needed:

The molar mass of O2 = 32.0 g/mol

-------------------

Step 3

By stoichiometry,

1 mole NH3 = 22.4 L NH3

1 mole O2 = 32.0 g O2

Procedure: We will work with volume and mass

4NH3 (g) + 9O2 (g) => 4NO3 + 6H2O (g)

4 x 22.4 L NH3 ---------- 9 x 32.0 g O2

X ----------- 5.3 g O2

X = 5.3 g O2 x 4 x 22.4 L NH3/9 x 32.0 g O2 = 1.65 L approx.

Answer: 1.65 L of NH3

To solve this problem we can use the Ideal gas law:

The problem give us de following information:

P1= 131kPa

V1=1.82L

T1=-30°C= 243.15 K

P2= 233 kPa

V2= 1.3L

Then we just have to solve for T2 and use the information provided:

Then the answer is T2=35.76°C