Chem 1C Midterm #2 Review

For a first-order reaction, a plot of __________ versus __________ is linear.

• ln [A]_t, t

• 1/[A]_t , t

• In [A]_t, 1/t

• [A]_t, t

• t, 1/[A]_t

Of the following, __________ will lower the activation energy for a reaction.

• increasing the concentrations of reactants

• adding a catalyst for the reaction

• raising the reaction temperature

• removing products as the reaction proceeds

• increasing the pressure

Consider the reaction:

S₂Cl_2(l) + CCl_4(l) → CS_2(g) + 3 Cl_2(g) ∆H˚ = 84.3 kJ

If the above reactants and products are contained in a closed vessel and the reaction system is at equilibrium, the number of moles of CS₂ can be increased by

• adding some S₂Cl₂

• removing some CCl₄

• decreasing the size of the reaction vessel

• increasing the temperature of the reaction system

• adding some Cl₂

Consider the general dissociation of an acid:

HA_(aq) ↔ H⁺_(aq) + A^-_(aq)

Select the true statement(s):

• Increasing the concentration of A- will increase HA dissociation

• The stronger the H-A bond, the weaker the acid

• The stronger the H-A bond, the stronger the acid

• The stronger the H-A bond, the easier it will dissociate

• The stronger the H-A bond, the harder it will be to dissociate

Which of the following ions will act as a weak base in water?

• ClO-

• Cl-

• NO3-

• OH-

• None of the above

Which of the following can be applied when solving for the pH of following dissociation:

HF_(aq)+ H₂O_(l) ↔ H₃O⁺_(aq) + F^-_(aq)

• Strong acid approximation, when percent ionization is >100%

• Weak acid approximation, when percent ionization is <5%

• Weak acid approximation, when percent ionization is >5%

• Weak base approximation, when percent ionization is <5%

Select from the following: the solution(s) in which you would have to consider the autoionization of water?

• HF and F-, at pH = 6.20

• HCN and CN-, at pOH = 6.40

• KF, at pH = 8.00

• None of the above

Which of the following statements is incorrect?

• HNO₃ added to a solution of CaC₂H₃O₂ lowers the pH

• NaBr added to a solution of HBr increases the pH

• NaC₂H₃O₂ added to a solution of HC₂H₃O₂ increases the pH

• CaCl₂ added to an HCl solution does not alter the pH

• KNO₃ added to an HCl solution does not alter the pH

A solution that contains a weak acid and its conjugate base in roughly equal concentrations is __________

• neither acidic or basic

• a heterogeneous mixture

• a half-acid solution

• neutral

• a buffer

The value of Ka for HSO₄^- is 1 × 10⁻². What is the value of Kb for SO₄²⁻?

• Kb = 1 × 10⁻¹²

• Kb = 1 × 10⁻⁸

• Kb = 1 × 10⁻²

• Kb = 1 × 10²

• Kb = 1 × 10⁵