Chemical Formulas Practice Test Questions

1 The simplest formula of a substance shows:
A. the actual number of atoms of each element in one molecule of a substance.
B. the elements that make up one molecule of the substance and the simplest whole number ratio between the atoms.

C. the number of molecules in a sample of the substance.

D. the molecular mass of the substance.

2 A compound is found to have a molecular mass of 90 atomic mass units and simplest formula of C₂H₅O. The molecular formula of the substance is:

Use atomic masses of C = 12 amu, H = 1 amu, O = 16 amu

A. C₃H₆O₃           B. C₄H₂₆O C. C₄H₁₀O₂ D. C₅H₁₄O

A substance of phosphorus (P) and oxygen (O) is found to have a mole ratio 0.4 moles of P for every mole of O.

The simplest formula for this substance is:

A. PO₂          B. P_0.4O        C. P₅O₂      D. P₂O₅

4 Which sample contains the greatest number of molecules?
Atomic masses are given in parentheses

A. 1.0 g of CH₄ (16 amu) B. 1.0 g of H₂O (18 amu)  

C. 1.0 g of  HNO₃ (63 amu) D. 1.0 g of N₂O₄ (92 amu)

5 A sample of potassium chromate, KCrO₄, contains 40.3% K and 26.8% Cr. The mass percent of O in the sample would be:

A. 4 x 16 = 64 B. 40.3 + 26.8 = 67.1 C. 100 - (40.3 + 26.8) = 23.9
D. The mass of the sample is needed to finish the calculation.

6 How many grams of oxygen are in one mole of calcium carbonate, CaCO₃?       Atomic mass of O = 16 amu

A. 3 grams B. 16 grams   C. 32 grams D. 48 grams

7 The ionic compound containing Fe³⁺ and SO₄^2- would have the formula:
A. FeSO₄ B. Fe₂SO₄   C. Fe₂(SO₄)₃    D. Fe₃(SO₄)₂

8 A compound with molecular formula Fe₂(SO₄)₃ would be called:
A. ferrous sulfate  B. iron(II) sulfate C. iron(III) sulfite D. iron(III) sulfate

9 The compound with molecular formula N₂O₃ would be called:
A. nitrous oxide B. dinitrogen trioxide C. nitrogen(III) oxide D. ammonia oxide

10 Copper sulfate crystals are actually crystals of copper sulfate pentahydrate. The molecular formula for copper sulfate pentahydrate is written as:

A. CuSO₄ · 5 H₂O B. CuSO₄ + H₂O C. CuSO₄  D. CuSO₄ + 5 H₂O

Electronic Structure Test Questions

1 The total number of electrons that can occupy the principle energy level n is: (a) 2 (b) 8  (c) n    (d) 2n²

2 For an electron with angular quantum number ℓ = 2, the magnetic quantum number m can have

(a) an infinite number of values (b) only one value (c) one of two possible values

(d) one of three possible values (e) one of five possible values

3 The total number of electrons allowed in a ℓ = 1 sublevel is
(a) 2 electrons (b) 6 electrons (c) 8 electrons (d) 10 electrons (e) 14 electrons

4 A 3p electron can have possible magnetic quantum number m values of

(a) 1, 2, and 3 (b) +½ or -½ (c) 0, 1, and 2 (d) -1, 0 and 1

(e) -2, -1, 0, 1 and 2

Which of the following set of quantum numbers would represent an electron in a 3d orbital?

(a) 3, 2, 1, -½ (b) 3, 2, 0, +½ (c) either a or b (d) neither a nor b

Calcium has an atomic number of 20. A stable calcium atom has an electronic configuration of

(a) 1s²2s²2p⁶3s²3p⁶4s²         (b) 1s²1p⁶1d¹⁰1f²   (c) 1s²2s²2p⁶3s²3p⁶3d²
     (d) 1s²2s²2p⁶3s²3p⁶                 (e) 1s²1p⁶2s²2p⁶3s²3p²

Phosphorus has an atomic number of 15. A stable phosphorus atom has an electronic configuration of

(a) 1s²1p⁶2s²2p⁵      (b) 1s²2s²2p⁶3s²3p³ (c) 1s²2s²2p⁶3s²3p¹4s²

(d) 1s²1p⁶1d⁷

8 The electrons with principle energy level n = 2 of a stable atom of boron (atomic number = 5) would have an electron arrangement of
(a) (↑ ↓) (↑) () ()             (b) (↑) (↑) (↑) ()
(c) () (↑) (↑) (↑)            (d) () (↑ ↓) (↑) ()
(e) (↑ ↓) (↑ ↓) (↑) (↑)

Which of the following electron arrangements does not represent an atom in its ground state?

   (1s) (2s) (2p) (3s)
(a) (↑ ↓) (↑ ↓) (↑ ↓) (↑ ↓) (↑ ↓) (↑)
(b) (↑ ↓) (↑ ↓) (↑ ↓) (↑ ↓) (↑ ↓) (↑ ↓)
(c)         (↑ ↓)        (↑ ↓)         (↑ ↓) (↑) (↑)

(d)         (↑ ↓)         (↑ ↓)          (↑ ↓) (↑ ↓) ()

10 Which of the following statements are false?
(a) the greater the energy transition, the greater the frequency
(b) the greater the energy transition, the shorter the wavelength
(c) the higher the frequency, the longer the wavelength
(d) the smaller the energy transition, the longer the wavelength

Equilibrium Constants Practice Test

1 An equilibrium constant with a value K > 1 means:
a. there are more reactants than products at equilibrium
b. there are more products than reactants at equilibrium
c. there are the same amount of products and reactants at equilibrium
d. the reaction is not at equilibrium

2 Equal amounts of reactants are poured into a suitable container. Given sufficient time, the reactants may be converted almost entirely to products if:

a. K is less than 1 b. K is greater than 1 c. K is equal to 1

D. K is equal to 0

3 The equilibrium constant for the reaction
H₂ (g) + I₂ (g) ↔ 2 HI (g)

would be:

a. K = [HI]²/[H₂][I₂]                b.K = [H₂][I₂]/[HI]² 

c.K= 2[HI]/[H₂][I₂]                 d. K = [H₂][I₂]/2[HI]

4 The equilibrium constant for the reaction
2 SO₂ (g) + O₂ (g) ↔ 2 SO₃ (g) would be:

a. K = 2[SO₃]/2[SO₂][O₂]      b. K = 2[SO₂][O₂]/[SO₃]
c. K = [SO₃]²/[SO₂]²[O₂]         d. K = [SO₂]²[O₂]/[SO₃]²

5 The equilibrium constant for the reaction
Ca(HCO₃)₂ (s) ↔ CaO (s) + 2 CO₂ (g) + H₂O (g)

would be:

a. K = [CaO][CO₂]²[H₂O]/[Ca(HCO₃)₂]

b. K = [Ca(HCO₃)₂]/[CaO][CO₂]²[H₂O]

c. K = [CO₂]²                                                                    d. K = [CO₂]²[H₂O]

6 The equilibrium constant for the reaction
SnO₂ (s) + 2 H₂ (g) ↔ Sn (s) + 2 H₂O (g)   would be:

a. K = [H₂O]²/[H₂]²                                             b. K = [Sn][H₂O]²/[SnO][H₂]²

 c. K = [SnO][H₂]²/[Sn][H₂O]²                  d. K = [H₂]²/[H₂O]²

For the reaction

H₂ (g) + Br₂ (g) ↔ 2 HBr (g), K = 4.0 x 10^-2. For the reaction
2 HBr (g) ↔ H₂ (g) + Br₂ (g)

K =:        a. 4.0 x 10^-2        b. 5     c. 25  d. 2.0 x 10^-1

8 At a certain temperature, K = 1 for the reaction
2 HCl (g) → H₂ (g) + Cl₂ (g)

At equilibrium, you can be certain that:
a. [H₂] = [Cl₂]      b. [HCl] = 2[H₂] c. [HCl] = [H₂] = [Cl₂] = 1

d. [H₂][Cl₂]/[HCl]² = 1

9 For the reaction: A + B ↔ C + D

6.0 moles of A and 5.0 moles of B are mixed together in a suitable container. When equilibrium is reached, 4.0 moles of C are produced.
The equilibrium constant for this reaction is:
a. K = 1/8   b. K = 8    c. K = 30/16        d. K = 16/30