Practice Questions

Relative atomic and molar masses are determined with a mass spectrometer utilizing the fact that

(A) the velocity of the paritcles can be accurately determined.
(B) a definite fraction of the particles is formed in a charged state.
(C) all particles with the same charge to mass ratio follow the same curved path.
(D) the force with which the accelerated particles strike a target can be measured.

C

When performing an acid-base titration, which procedure would NOT introduce an error into the experimental results

(A) adding an unmeasured amount of water to the carefully measured acid sample which is being titrated.
(B) failing to rinse the burettes with the appropriate reactants after cleaning and rinsing with water.
(C) failing to remove bubbles of air from the tips of the burettes before beginning the titration.
(D) using an indicator that changes color at a pH considerably removed from the pH at the equivalence point of the titration.

A

Seawater contains a fairly high concentration of Mg²⁺(aq) ion, about 0.05 M. Seawater therefore would not be expected to contain very large concentrations of

(A) Cl¯
(B) SO₄²¯
(C) K⁺
(D) OH¯

D

500 mL of 0.020 M BaCl₂(aq) is added to 500 mL of 0.020 M NaF(aq). K_sp = 2 x 10¯⁶ for BaF₂ in water.

(A) The solutions mix without reaction
(B) A precipitate of BaF₂(s) is formed when the solutions are mixed
(C) Undissolved BaCl₂ solid dissolves when the solutions are mixed
(D) The concentrations of all the ions in the final solution are 2 x 10¯⁶ M.

A

Which aqueous solution should be neutral?

(A) NH₄Cl
(B) Na(ClO₄)₂
(C) KCN
(D) NaHSO₄

B

Carbon dioxide is a gas at room temperature while silicon dioxide is a high-melting solid. The best explanation of this difference is that

(A) Si has more electrons than C
(B) the atoms in CO₂ are bound by covalent bonds while SiO₂ is an ionic compound
(C) van der Waals' forces are stronger in SiO₂
(D) CO₂ consists of discrete molecules while in SiO₂ atoms are joined by a network of covalent bonds

D

Carbonic acid (aqueous carbon dioxide) is a diprotic acid which dissociates according to the steps

H2CO3 + H2O <===> HCO3¯ + H3O+	Ka1 = 4.2 x 10¯7
HCO3¯ + H2O <===> CO32¯ + H3O+	Ka2 = 4.8 x 10¯11

What is the concentration of carbonate ion in a saturated solution of H₂CO₃ that is 0.037 M?

(A) 5.2 x 10¯¹⁹ M
(B) 4.8 x 10¯¹¹ M
(C) 7.6 x 10¯⁸ M
(D) 4.2 x 10¯⁷ M

B

The advice is often given that the bottom of a meniscus should be used in reading a volumetric instrument. In which of the following operations would it make no difference what part of the meniscus was used?

(A) Making a solution of known concentration using a volumetric flask.
(B) Transferring 5.00 ml of a solution using a transfer pipet.
(C) Transferring 23.7 of a solution using a burret.
(D) Measuring 65 ml using a measuring cylinder

C

When ammonia is added to a solution, a brown precipitate forms and the suernatant liquor turns deep blue. Which of the following best explains these phenomena?

(A) The solution contains Cu²⁺ and Ni²⁺
(B) The solution contains Fe³⁺ and Cu²⁺
(C) The solution contains Ni²⁺ and Fe³⁺
(D) The solution contains Fe²⁺ and Fe³⁺

B

Which salt is the least soluble?

(A) AgF
(B) AgCl
(C) AgBr
(D) AgI

D

Which salt is least likely to be dissolved in water if sulfuric acid is added to the water?

(A) CaCO₃
(B) BaSO₄
(C) Cu(OH)₂
(D) NaCl

B

Bleaching powder reacts with iodide ion according to the following unbalanced equation:

OCl¯ + I¯ + H⁺ <===> I₂ + Cl¯ + H₂O

A 0.6000 g sample of bleaching powder requires 35.24 mL of 0.1084 N Na₂S₂O₃ to titrate the liberated iodine. The percentage of Cl in the sample is

(A) 22.58% Cl
(B) 5.15% Cl
(C) 11.29% Cl
(D) 45.16% Cl

C

Expressed to the appropriate number of significant figures, the result of the calculation [(5.031-4.96)(2.38)] ÷ 3.91

(A) 0.04
(B) 0.043
(C) 0.0432
(D) 0.04322

A

Sodium nitrate, heated in the presence of an excess of hydrogen, forms water according to the two-step process

2 NaNO3 ---> 2 NaNO2 + O2

2 H2 + O2 ---> 2 H2O

How many grams of sodium nitrate are required to form 9 grams of water?

(A) 21.3
(B) 42.5
(C) 69.0
(D) 85.0

B

Which statement desribing chemical equilibrium is NOT correct?

(A) A system at chemical equilibrium has a constant mass.
(B) A system in chemical equilibrium acts so as to oppose slight disturbances.
(C) Forward and reverse reactions proceed at the same rate in a system at chemical equilibrium.
(D) Reactant and product concentrations vary with time in a system at chemical equilibrium.

D

A "buffered" solution

(A) contains an insoluble solid.
(B) resists a change in its pH.
(C) contains a salt of a strong acid and a strong base.
(D) contains a concentrated strong acid

B