Chemistry II - test 2
Calculate the value of [N2]eq if [H2]eq = 2.0 M, [NH3]eq = 0.5 M, and Kc = 2. N2(g) + 3 H2(g) ⇌ 2 NH3(g) (2 sig figs)
0.016 M
Determine the solubility, in g/L, for CuC2O4(s) in pure water. Ksp for is 2.9 × 10-8. (2 sig figs)
0.026 g L-1
Consider the following reaction: CH4(g) + 2 H2S(g) ⇌ CS2(g) + 4 H2(g) A reaction mixture initially contains 0.50 M CH4 and 0.75 M H2S. If the equilibrium concentration of H2 is 0.44 M, find the equilibrium constant (Kc) for the reaction.
0.038
Determine the value of Kc for the following reaction if the equilibrium concentrations are as follows: [N2]eq = 1.5 M [H2]eq = 1.1 M [NH3]eq = 0.47 M N2(g) + 3 H2(g) ⇌ 2 NH3(g)
0.11
What is the [CH3CO2-]/[CH3CO2H] ratio necessary to make a buffer solution with a pH of 4.44? Ka = 1.8 × 10-5 for CH3CO2H.
0.50:1
Calculate the concentration of H3O⁺ in a solution that contains 5.5 × 10-5 M OH⁻ at 25°C. Identify the solution as acidic, basic, or neutral. (scientific notation, 2 sig figs)
1.8 × 10-10 M, basic
Determine the pH of a 0.461 M C6H5CO2H M solution if the Ka of C6H5CO2H is 6.5 × 10-5.
2.26
Determine the Ka for CH3NH3⁺ at 25°C. The Kb for CH3NH2 is 4.4 × 10-4. (scientific notation, 2 sig figs)
2.3 × 10^-11
The equilibrium constant is given for one of the reactions below. Determine the value of the missing equilibrium constant. H2(g) + Br2(g) ⇌ 2 HBr(g) Kc = 3.8 × 104 2 HBr(g) ⇌ H2(g) + Br2(g) Kc = ?
2.6 × 10^-5
Determine the molar solubility of MgCO3 in pure water. Ksp (MgCO3) = 6.82 × 10^-6. (scientific notation, 3 sig figs)
2.61 × 10-3 M
A container of orange juice at 25°C has a hydronium concentration of 1.78 × 10-3M. What is the pH of the juice?
2.75
Calculate the pH of a buffer that is 0.225 M HC2H3O2 and 0.162 M KC2H3O2. The Ka for HC2H3O2 is 1.8 × 10-5.
4.60
Consider the following reaction, equilibrium concentrations, and equilibrium constant at a particular temperature. Determine the equilibrium concentration of SO2(g). 2 SO2(g) + O2(g) ⇌ 2 SO3(g) Kc = 1.7 × 108 [SO3]eq = 0.0034 M [O2]eq = 0.0018 M
6.1 × 10^-6 M
Dinitrogen tetroxide partially decomposes according to the following equilibrium: N2O4(g) → 2NO2(g) A 1.000-L flask is charged with 8.00 × 10-3 mol of N2O4. At equilibrium, 5.04 × 10-3 mol of N2O4 remains. Keq for this reaction is
6.94 × 10^-3
Calculate the hydroxide ion concentration in an aqueous solution with a pH of 9.85 at 25°C. (scientific notation, 2 sig figs)
7.1 × 10^-5 M
Determine the Ka of an acid whose 0.294 M solution has a pH of 2.80. (scientific notation, 2 sig figs)
8.5 × 10^-6
If a chemist wishes to prepare a buffer that will be effective at a pH of 3.00 at 25°C, the best choice would be an acid component with a Ka equal to 9.10 × 10-6. 9.10 × 10-10. 9.10 × 10-4. 9.10 × 10-8. 9.10 × 10-2.
9.10 × 10^-4.
Which of the following is TRUE? - An effective buffer has very small absolute concentrations of acid and conjugate base. - An effective buffer has a [base]/[acid] ratio in the range of 10 - 100. - None of these are true. - A buffer is most resistant to pH change when [acid] = [conjugate base] - A buffer can not be destroyed by adding too much strong base. It can only be destroyed by adding too much strong acid.
A buffer is most resistant to pH change when [acid] = [conjugate base]
Which one of the following statements is TRUE? - All of these are true. - A buffer does not change pH when strong base is added. - A buffer can absorb an unlimited amount of base. - A buffer is an aqueous solution composed of two strong bases. - A buffer resists pH change by neutralizing added acids and bases.
A buffer resists pH change by neutralizing added acids and bases.
________ is the active component in vinegar.
CH3COOH
What is the conjugate acid of HCO3⁻ ?
H2CO3
Which of the following is not a conjugate acid-base pair? All of these are conjugate acid-base pairs. NH4+/NH3 H3O⁺/OH⁻ H2SO3/HSO3⁻ C2H3O2⁻/HC2H3O2
H3O⁺/OH⁻
Which of the following solutions would have the highest pH? Assume that they are all 0.10 M in acid at 25∘C. The acid is followed by its Ka value. HClO2, 1.1 × 10-2 HF, 3.5 × 10-4 HCN, 4.9 × 10-10 HNO2, 4.6 × 10-4 HCHO2, 1.8 × 10-4
HCN, 4.9 × 10^-10
What is the conjugate base of H2PO4⁻ ?
HPO4^2-
Which of the following statements is TRUE? - If Q > K, it means the reverse reaction will proceed to form more reactants. None of these are true. - If Q < K, it means the reverse reaction will proceed to form more reactants. - If Q = K, it means the reaction is not at equilibrium. - All of these are true.
If Q > K, it means the reverse reaction will proceed to form more reactants.
Consider the following reaction at equilibrium. What effect will raising the pressure of the system from 5 atm to 8 atm? 2 NH3(g) ⇌ N2(g) + 3 H2(g) It will shift to the right It will slow down the reaction It will shift to the left It will speed up the reaction It will have no effect
It will shift to the left
Which of the following statements is FALSE? - None of these are false - When K << 1, the reverse reaction is favored and the forward reaction does not proceed to a great extent. - When K >> 1, the forward reaction is favored and essentially goes to completion. - When K ≈ 1, neither the forward or reverse reaction is strongly favored, and about the same amount of reactants and products exist at equilibrium. - K >> 1 implies that the reaction is very fast at producing products.
K >> 1 implies that the reaction is very fast at producing products.
Which of the following is TRUE? - An indicator is not pH sensitive. - None of these are true. - The equivalence point is where the amount of acid equals the amount of base during any acid-base titration. - A titration curve is a plot of pH vs. the [base]/[acid] ratio. - At the equivalence point, the pH is always 7.
The equivalence point is where the amount of acid equals the amount of base during any acid-base titration.
Consider the following reaction at equilibrium. What effect will adding more SO3 have on the system? SO2(g) + NO2(g) ⇌ SO3(g) + NO(g) - The equilibrium constant will decrease. - The reaction will shift in the direction of reactants. - The reaction will shift to decrease the pressure. - The reaction will shift in the direction of products. - No change will occur since SO3 is not included in the equilibrium expression.
The reaction will shift in the direction of reactants.
Consider the following reaction at equilibrium. What effect will reducing the volume of the reaction mixture have on the system? Xe(g) + 2 F2(g) → XeF4(g) - The equilibrium constant will increase. - No effect will be observed. - The reaction will shift to the right in the direction of products. - The reaction will shift to the left in the direction of reactants. - The equilibrium constant will decrease.
The reaction will shift to the right in the direction of products.
If the pKa of HCHO2 is 3.74 and the pH of an HCHO2/NaCHO2 solution is 3.11, which of the following is TRUE? [HCHO2] < [NaCHO2] [HCHO2] = [NaCHO2] [HCHO2] > [NaCHO2] It is not possible to make a buffer of this pH from HCHO2 and NaCHO2. [HCHO2] << [NaCHO2]
[HCHO2] > [NaCHO2]
The following reaction is exothermic. Which change will shift the equilibrium to the left? 2 SO2(g) + O2(g) ⇌ 2 SO3(g) all of these increase volume raising the temperature none of these decrease pressure
all of these
Give the characteristics of a strong acid. all of these are true has a weaker bond to hydrogen has a polar bond has equilibrium far to the right ionizes completely in aqueous solutions
all of these are true
Stalactites and stalagmites form as ________ precipitates out of the water evaporating in underground caves. calcium carbonate sodium bicarbonate sodium chloride hydrochloric acid sodium hydroxide
calcium carbonate
Which of the following weak acids has the strongest conjugate base? nitrous acid, Ka = 4.5 × 10-4 hydrocyanic acid, Ka = 4.0 × 10-10 acetic acid, Ka = 1.8 × 10-5 dihydrogen phosphate ion, Ka = 6.2 × 10-8 benzoic acid, Ka = 6.3 × 10-5
hydrocyanic acid, Ka = 4.0 × 10-10
Chemical equilibrium is the result of - formation of products equal in mass to the mass of the reactants. - opposing reactions attaining equal rates. - a loss of pressure in the system. - stoppage of further reaction. - all of the reactants being converted into products.
opposing reactions attaining equal rates
When titrating a strong monoprotic acid with KOH at 25°C, the - pH will be greater than 7 at the equivalence point. - pH will be equal to 7 at the equivalence point. - pH will be less than 7 at the equivalence point. - titration will require more moles of base than acid to reach the equivalence point. - titration will require more moles of acid than base to reach the equivalence point.
pH will be equal to 7 at the equivalence point.
When titrating a weak monoprotic acid with NaOH at 25°C, the - titration will require more moles of acid than base to reach the equivalence point. - pH will be less than 7 at the equivalence point. - pH will be equal to 7 at the equivalence point. - titration will require more moles of base than acid to reach the equivalence point. - pH will be greater than 7 at the equivalence point.
pH will be greater than 7 at the equivalence point.
When titrating a monoprotic strong acid with a weak base at 25°C, the - pH will be 7 at the equivalence point. - pH will be greater than 7 at the equivalence point. - pH will be less than 7 at the equivalence point. - titration will require more moles of the base than acid to reach the equivalence point. - titration will require more moles of acid than base to reach the equivalence point.
pH will be less than 7 at the equivalence point.
Identify a good buffer. - small amounts of both a weak acid and its conjugate base - significant amounts of both a strong acid and a strong base - significant amounts of both a weak acid and its conjugate base - small amounts of both a strong acid and a strong base - significant amounts of both a weak acid and a strong acid
significant amounts of both a weak acid and its conjugate base
