The Position of Equilibrium for the Reaction

Leader: Olivia Exam 2 Review Course: Chem 178 Supplemental Instruction Instructor: Miller Iowa State University Date:

The position of equilibrium for the reaction

ZnO(s) + H2(g) Zn(s) + H2O(g) does not depend upon which of the following (pick multiple): (1) concentration of ZnO(s) (2) concentration of H2(g) (3) concentration of Zn(s) (4) concentration of H2O(g) (5) the value of Kc?

Which way will the following reactions, initially at equilibrium, shift when the temperature is decreased at constant pressure?

1.) 2C2H2(g) + 5O2(g) 4CO2(g) + 2H2O(l) ΔH = -1297 kJ 2.) CO2(g) O2(g) + C(s) ΔH = +393 kJ 3.) 4Fe(s) + 3O2(g) 2Fe2O3(s) ΔH = -1644 kJ

A substances that donates a proton in a chemical reaction can be described as: a.) Bronsted-Lowry acid b.) Bronsted-Lowry base c.) Conjugate base d.) Arrhenius acid e.) Arrhenius base

A solution with a [OH-] = 5.5x10-5 at 25 0C is a.) Acidic b.) Basic c.) Neutral

Calculate the pH in the above problem.

What is the value of Kc for the following reaction if the equilibrium concentrations are [A] = 0.60 M [B] = 0.35 M [C] = 0.55 M?

2 A (aq) + B (aq) ⇌ 2 C (aq)

1060 Hixson-Lied Student Success Center v 515-294-6624 v [email protected] v http://www.si.iastate.edu Initially 0.035 moles of SO2, 0.5 moles of SO2Cl2, and 0.08 moles of Cl2 are combined in a 5 liter flask. What is the value of Q and which direction will the reaction proceed to establish equilibrium?

SO2Cl2 (g) ⇄ SO2 (g) + Cl2 (g) Kc = 0.078

Which of these conjugate acid-base pairs will NOT function as a buffer? - a. CH3COOH and CH3COO b. HCl and Cl- - 2- c. HCO3 and CO3 d. All of the above will function as a buffer

Which one of the following binary compounds would you expect to be the most acidic? a. H2S or HCl b. HBr or HF c. HClO4 or HClO3

Label the following as a SA, WA, or negligible and write its conjugate base. a. HCOOH b. HF c. + NH4

The pH of a 0.15 M weak base B is 9.25. What is Kb for B? B is an arbitratry weak base, use the equation: B (aq) + H2O(l) equil BH+ (aq) + OH- (aq)

-5 -8 Given the Kb for ammonia is 1.8x10 and for hydroxylamine is 1.1x10 , which is the stronger base? a. Which conjugate acid is stronger?

b. Calculate the Ka for the conjugate acids Which of the following 0.1 M solutions has the smallest pH? a. NH4Cl b. NaNO3 c. BaI2 d. NH3 e. Na2ClO3

-8 Determine the pH of an initial 0.95 M solution of HOCl (Ka= 3.0x10 )

-5 What is the pH of a solution containing 0.8M NH3 and 1.0M of NH4Cl? Kb(NH3)=1.77x10

You are asked to prepare a pH=4.00 buffer starting from 1.50 L of 0.0200 M solution of benzoic acid (C6H5COOH) and any amount of sodium benzoate (C6H5COONa) in 1.20 L. a. What is the pH of the benzoic acid solution prior to adding sodium benzoate?

b. How many gram of sodium benzoate should be added to prepare the buffer?

The ______the acid, the ______the conjugate base.

The ______the pKa of the conjugate acid, the ______the base.

Acidity _____ with increasing positive charge on an atom. Across the periodic table acidity increases with ______, down the periodic table acidity increases with ______.

Classify the solutions as acids or bases.

Rank these acids from weakest to strongest:

- - CF3COOH HCO3 H2PO4 CH3COOH

What structural features of a molecule may effect the pKa of an acid?

Calculate the pH of a buffer that is 0.105 M in NaHCO3 and 0.125 M in Na2CO3.

Calculate the pH of a buffer formed by mixing 65 mL of 0.20 M NaHCO3 with 75mL of 0.15 M of Na2CO3.