A)    7

B)    5

C)    9

D)    4

Correct Answer: Option C - 9

4Al + 3O₂ = 2Al₂O₃.

Coefficients are the numbers in front of the element symbols. Add 4 + 3 + 2 to get 9.

Hence, options A, B and D are incorrect.

A)    N₂O

B)    NO

C)    N₂O₃

D)    NO₂

Correct Answer: Option A - N₂O

The oxidation number for Oxygen (O) is -2 and the oxidation number for Nitrogen (1) is +1. Since this is a compound, the oxidation numbers of the atoms in the compound must equal zero. In N₂O, note how N (2)( +1) or a +2 charge will cancel out the -2 charge of one oxygen ion.

Hence, options B, C and D are incorrect.

2CO(g) + O₂(g) → 2CO₂(g)

What is the mole ratio of CO(g) to CO₂(g) in this reaction?

A)    2:1

B)    1:1

C)    1:2

D)    3:2

Correct Answer: Option B - 1:1

A mole is the number of protons or neutrons needed to make up one gram.

1 mole = 6.02x10²³

The ratio of the moles of one reactant or product to the moles of another reactant of product in the balanced equation for a chemical reaction is called a mole ratio.

2CO(g) → 2CO₂(g)

= 2 → 2

= 2: 2

= 1:1

Hence, the options A, C and D are incorrect.

A)    5 moles

B)    3 moles

C)    6 moles

D)    2 moles

Correct Answer: Option C - 6 moles

From the above equation it is inferred that 1 unit of hydrogen can combine with 1 unit of chlorine to form 2 units of hydrochloric acid.

1 + 1 = 2

Hence, 3 moles of hydrogen can be completely consumed by 3 moles of chlorine to for 6 moles of hydrochloric acid.

3 + 3 = 6

Hence, options A, B and D are incorrect.

A)    138 g

B)    99 g

C)    106 g

D)    67 g

Correct Answer: Option A - 138 g

The unified atomic mass unit (u), or dalton (Da) or, sometimes, universal mass unit, is a unit of mass used to express atomic and molecular masses. It is the approximate mass of a hydrogen atom, a proton, or a neutron.

The precise definition is that it is one twelfth of the mass of an isolated atom of carbon-12 (¹²C) at rest and in its ground state.

1 u = 1/NA gram = 1/ (1000 NA) kg   (where NA is Avogadro's number)

1 u = 1.660538782(83)×10^-27 kg = 931.494028(23) MeV/c²

• Atomic mass of K: 39.0983 amu
• Atomic mass of C: 12.0107 amu
• Atomic mass of O: 15.9994 amu

Hence from the above equation, we have the following calculation

K =39 x 2 = 78 g;

C =12 x 1 = 12 g;

O =16 x 3 = 48 g.

Total is 78 + 12 + 48 or 138 g.

Hence, options B, C and D are incorrect.

A)    6.02 moles

B)    1.5 moles

C)    2.00 moles

D)    9.03 moles

Correct Answer: Option B - 1.5 moles

A mole is the number of protons or neutrons needed to make up one gram.

1 mole = 6.02x10²³

Divide 9.03 x 10²³ by 6.02 x 10²³ to find the number of moles of hydrogen gas.

9.02 x 10²³ / 6.02 x 10²³ = 1.5 moles

Hence, options A, C and D are incorrect.

A)    44 g

B)    66 g

C)    22 g

D)    80 g

Correct Answer: Option C - 22 g

Atomic mass of carbon is 12 and atomic mass of oxygen is 16

Hence, the gram mass of CO₂ = 12 + 2 (16) = 44

Thus, one mole of CO₂ has a gram mass of 44 grams and contains 1 mole of molecules (6.02 x 10²³).

You are given 3 x 10²³ equals 1/2 the mass of 1 mole of CO2 or 1/2 x 44 = 22 g.

Hence, options A, B and D are incorrect.

A)    2.00 M

B)    1.00 M

C)    3.00 M

D)    5.00 M

Correct Answer: Option A - 2.00 M

Molar concentration (also called molarity, amount concentration or substance concentration) is a measure of the concentration of a solute in a solution, or of any molecular, ionic, or atomic species in a given volume

Firstly find the moles of solute using the formula: mass of solute (g) divided by formula mass of solute

Now divide the moles of solute by volume of solution in liters M / V. Or if you know the moles of solute,

Molarity = moles of solute divided by volume of solution in liters.

KF has a formula mass of 39 + 19 or 58 g/mole. Since 116 grams are given, 116g / 58g/mole = 2 moles of solute.

To find the Molarity, take 2 moles of solute and divide by 1 L of solution. 2 moles / 1 L = 2.00 M solution

Hence options B, C and D are incorrect.

A)    44.8 L of He

B)    32. 0 L of H₂

C)    28.0 L of N₂

D)    22.4 L Ar

Correct Answer: Option B - 32. 0 L of H₂

Avogadro's law (sometimes referred to as Avogadro's hypothesis or Avogadro's principle) is a gas law named after, Avagadro hypothesized that:

Equal volumes of ideal or perfect gases, at the same temperature and pressure, contain the same number of particles, or molecules. Thus, the number of molecules in a specific volume of gas is independent of the size or mass of the gas molecules.

As an example, equal volumes of molecular hydrogen and nitrogen would contain the same number of molecules, as long as they are at the same temperature and pressure and observe ideal or perfect gas behavior. In practice, for real gases, the law only holds approximately, but the agreement is close enough for the approximation to be useful.

Hence, options A, C and D are incorrect.

A)    Hydrogen sulfate

B)    Ammonium sulfide

C)    Ammonium sulfate

D)    Hydrogen sulfide

Correct Answer: Option D - Hydrogen sulfide

A binary compound is a chemical compound that contains exactly two different elements.

Hydrogen sulfide (or hydrogen sulphide) is the chemical compound with the formula H₂S. This colorless, toxic and flammable gas is partially responsible for the foul odor of rotten eggs and flatulence.

Incorrect Options

Hydrogen sulfate has 3 kinds of atoms (H, S, O). Its also referred as sulphuric acid. Sulfuric (or sulphuric) acid, H₂SO₄, is a strong mineral acid.

Ammonium sulphide has 3 kinds (N, H, S). Ammonium sulfide, also known as diammonium sulfide, is an unstable salt with the formula (NH₄)₂S

Ammonium sulfate has 4 kinds (N, H, S, O). Ammonium sulfate (NH4)2SO4, is an inorganic salt