Chemistry Final

Calculate the pOH of a solution that contains 3.9 x 10^-4 M H3O+ at 25C A)0.59 B)9.14 C)10.59 D)4.59 E)3.31

3.9 X 10 -4 M H3O+ pH= -log ( 3.9 X 10 -4 M H3O+) = 3.4089 14= pH+pOH pOH= 14- pH 14 - 3.4089 = pOH= 10.59 C) 10.59

Which of the following solutions is a good buffer system? A) a solution that is 0.10 M HCl and 0.10 M NH4+ B) a solution that is 0.10 M HC2H3O2 and 0.10 M LiC2H3O2 C) A solution that is 0.10M NaOH and 0.10M KOH D) A solution that is 0.10M HF and 0.10 M NaC2H3O2 E) none of the above

A buffer solution contains a weak acid ( or base) and the conjugate base ( or acid) :A solution that is 0.10 M HC2H3O2 and 0.10 M LiC2H3O2.The solution has the same amount of moles in the weak acid and conjugate base . It is a good buffer.

Which of the following is an Arrhenius base? A) NaOH B) CH3OH C) LiCl D) CH3CO2H E) more than one above

A)

A 100 ml sample of 0.10 M ca(OH)2 is titrated with 0.10 M HBr. Determine the pH of the solution after the addition of 300 ml HBr A) 1.60 B) 1.12 C)12.40 D)1.00 E) 1.30

A) 1.60

The Eq constantant is given for one of the reactions below. Determine the value of the missing eq constant H2(g) + Br2(g) <---> 2 HBr(g) Kc = 3.8 x 10^4 2 HBr(g) <---> H2(g) + Br2(g) Kc = ? A) 2.6 x 10^-5 B) 1.9 x 10^4 C) 5.3 x 10^-5 D) 6.4 x 10^-4 E) 1.6 x 10^3

A) 2.6 x 10^-5

Calculate the pH of a buffer that is 0.058 M HF and o.o58 M LiF. The ka for HF is 3.5 x 10.^-4 A) 3.46 B) 4.69 C) 2.86 D) 9.31 E) 10.54

A) 3.46

Which one of the following statements is TRUE? A) A buffer resists pH change by neutralizing added acids and bases B) A buffer can absorb an unlimited amount of acid or base C) A buffer is an aqueous solution composed of two weak acids D) A buffer does not change pH when strong acid or base is added E) non of the above

A) A buffer resists pH change by neutralizing added acids and bases

Which of the following is a Lewis acid A) BCl3 B) CHCl3 C) NH3 D) CH4 E) none of the above

A) BCl3

Identify a homogenous catalyst A) H2SO4 with concentrated HCl B) N2 and H2 catalyzed by Fe C) Pt with methane D) pd in H2 gas E) SO2 over vanadium (v) oxide

A) H2SO4 with concentrated HCl

Which of the following is NOT a conjugate acid-base pair? A) H3O+/OH- B) C2H3O2-/HC2H3O2 C) H2SO3/HSO3- D) NH4+/NH3 E) All of the above are conjugate acid -base pairs

A) H3O+/OH-

Given the following proposed mechanism, predict the rate law for the overall reaction A2 + 2B --> 2AB (overall reaction) Mechanism A2<--->2A fast A + B -->AB slow A) Rate = K [A2]^1/2 [B] B) Rate = K [A2][B] C) Rate = k[A2] D) Rate = k[A][B] E) Rate = K[A2][B]^1/2

A) Rate = K [A2]^1/2 [B]

Which of the following is a Bronsted-Lowry acid? A) Ch4 B) NH4+ C) Br2 D) NH3 E) NH2-

B) NH4+

In which of the following reactions will Kc = Kp? A) 4NH3 (g) + 3 O2(g) <---> 2 N2 (g) + 6 H2O(g) B) SO3(g) + NO(g) <---> SO2(g) + NO2(g) C) 2 N2(g) + O2(g) <---> 2 N2O(g) D) 2 SO2(g) + O2(g) <---> 2SO3(g) E) Non of the above reactions have Kc=kp

B) SO3(g) + NO(g) <---> SO2(g) + NO2(g)

What is the conjugate acid of HCO3- A)H20 B)H2CO3 C)CO32- D)OH- E)H3O+

B)H2CO3

What is the Kw of pure water at 50C, if the pH is 6.630? A) 2.34 x 10^-7 B)2.13 x 10^-14 C) 5.50 x 10^-14 D) 1.00 x 10^-14

C) 5.50 x 10^-14 [H+] x [OH-] = Kw pH = -log([H+]) In pure water, [H+] = [OH-], therefore: Kw = [H+]^2 pH = -log [H+] = 6.630 [H+] = 1 x 10^-6.63 Kw = [H+]^2 = (1 x 10^-6.63)^2 = 5.5 x 10^-14

What is the pH of pure water at 40C if the Kw at this temperature is 2.92 x 10^14? A) 7.000 B) 0.465 C) 6.767 D) 7.233 E) 8.446

C) 6.767 Kw = 2.92 * 10^-14 We know that Kw = [OH-] * [ H3O+ ] For water [OH-] = [H3O+ ] So Kw = [OH-] * [ H3O+] = [ H3O+ ] * [ H3O+] = [ H3O+] 2 2.92* 10^-14 = [ H3O+ ]2 ==> [ H3O+ ] = √(2.92*10^-14) = 1.7*10^-7 M So t he \left[ {{\rm{H}}_3 {\rm{O}}^ + } \right] of pure water at body temperature = 1.7*10^-7M pH = - log [ H3O+ ] = log ( 1.7*10^-7 ) = 6.76

Identify the Weakest acid A)HCl B)HI C)HF D)HBr E) not enough info

C) HF

Which of the following statements is TRUE? A) a strong acid is composed of a proton and an anion that have a very strong attraction for one another B) A strong acid has a strong conjugate base C) The conjugate base of a very weak acid is stronger than the conjugate base of a strong acid D) A weak base is composed of a cation and an anion with a very weak attraction between them E) None are true

C) The conjugate base of a very weak acid is stronger than the conjugate base of a strong acid

Consider the following reaction and its EQ constant SO2(g) + NO2(g) <---> SO3(g) + NO(g) kc=0.33 A reaction mixture contains 0.39 M SO2, 0.14 M NO2, 0.11 M SO3 and 0.14 M NO. Which of the following statements is TRUE concerning this system? A) The reaction quotient will decrease B) The eq constant will decrease C) The reaction will shift in the direction of products D) The reaction will shift in the direction of the reactants The system is at eq

C) The reaction will shift in the direction of products

You wish to prepare an HC2H3O2 buffer with a pH of 4.24. If the pKa is 4.74, what ratio of c2H3O2-/HC2H3O2 must you use? A) 2.0 B) 2.8 C)0.32 D) 0.50 E) 0.10

C)0.32

Calculate the concentration of OH- in a solution that contains 3.9 x 10^-4 M H3O+ at 25 C. Identify the solution as acidic, basic or neutral A) 2.7 x 10^-2, basic B) 3.9 x 10 ^4, neutral C) 2.6 x 10^11, basic D) 2.6 x 10^ 11, acidic E) 2.6 x 10^ 2, acidic

D) 2.6 x 10^ 11, acidic

Which of the following statements is true? A) The EQ constant for the forward reaction is equal to the equilibrium constant for the reverse reaction B) A reaction quotient (Q) larger than the equilibrium constant (K) means that the reaction will favor the production of more products C) Dynamic eq indicates that the amount of reactants and products are equal D) Dynamic eq occurs when the rate of the forward reaction equals the rate of the reverse reaction E) All of the above are true

D) Dynamic eq occurs when the rate of the forward reaction equals the rate of the reverse reaction

Which of the following solutions would have the highest pH? Assume that they are all 0.10 M in acid at 25C. The acid is followed by its Ka value. A) HNO2, 4.6 x 10^-4 B) HCHO2, 1.8 x 10^-4 C) HF, 3.5 x 10^-4 D) HCN, 4.9 x 10^-10 E) HClO2, 1.1 x10^-2

D) HCN, 4.9 x 10^-10 large Ka value indicates a stronger acid (more of the acid dissociates) and small Ka value indicates a weaker acid (less of the acid dissociates). As HCN has lowest Ka value, it indicates a weaker acid (less of the acid dissociates). Thus HCN solutions has highest pH than other solutions

The following reaction is exothermic. Which change will shift the eq to the left 2SO2(gO + O2(g) <---> 2 SO3(g) A) decrease pressure B) increase volume C) raising the temperature D) all of the above E) non of the above

D) all of the above

Which of the following compounds will have the highest molar solubility in pure water? A) PbS, Ksp = 9.04 x 10^-29 B) AGI, Ksp = 8.51 x 10^-17 C) MgCO3, Ksp = 6.82 x 10^-6 D) FeS, Ksp = 3.72 x 10-19 E) PbSO4, ksp = 1.82 x 10-^8

For all salts, Ksp = [cation][anion] = x2 where x is the molar solubility. Ksp, x2 and x are highest for MgCO3 C)MgCO3, Ksp = 6.82 x 10^-6

Determine the value of Kc for the following reaction if the eq concentrations are as follows: [N2]eq = 3.6 M, [O2]eq = 4.1 M, [N2O]eq = 3.3 x 10 ^-18 M 2N2(g) + O2(g) <---> 2N2O(g) A) 2.0 x 10^-37 B) 4.9 x 10^-17 C) 4.5 x10 ^18 D) 5.0 x 10^36 E) 2.2 x 10^-19

Kc = [N2O]^2 / [N2]^2 * [O2] Kc = (3.3 × 10-18 M)^2 / (3.6)^2 * (4.1) Kc = 2.05 x 10^-37 A) 2.0 x 10^-37

A solution containing AgNO3 is mixed with a solution of NACl to form a solution that is 0.10 M in Ag NO3 and 0.075 in NaCl. What will happen once these solutions are mixed Ksp (AgCl) = 1.77 x 10^-10 A) Nothing will happen since Nacl and AgNO3 B) Silver Chloride will precipitate out of solution, leaving a saturated AgCl solution C) Silver chloride will precipitate out of solution, leaving an unsaturated solution of AgCl D) Nothing will happen since the molar solubility of AgCl is higher than the solution concentrations E) there is not enough information to say anything about this solution

Ksp = [Ag+][Cl-] = 1.77x10^-10 Q = [Ag+][Cl-] = (0.10)(0.075) = 7.5x10^-3 Ksp < Q B) Silver chloride will precipitate out of solution, leaving a saturated AgCl solution

Determine the POH in a 0.235M NaOH solution A) 13.37 B) 13.76 C) 12 D) 0.24 E) 0.63

NaOH ionizes 100% in aqueous solution, so [OH] = 0.235M in this case. pOH = -log[OH-] pOH = -log[0.235] pOH = -(-0.63) pOH = 0.63 (option E)

Identify the diprotic acid A) HClO4 B) H2SO4 C) HCl D) HNO3 E) CH3COOH

diprotic acid is a class of Arrhenius acids which are capable of donating two protons or hydrogen cations B) H2SO4

Give the direction of the reaction, if K>>1 A) if the temperature is raised, then the forward reaction is favored B) The reverse reaction is favored C) If the temperature is raised, then the reverse reaction is favored D) Neither direction is favored

if the K>>1 , the reaction is favored in forward direction

Calculate the pH of a solution formed by mixing 250 ml of 0.15 M NH4CL with 100 ml of 0.20 M NH3. The kb for NH3 is 1.8 x 10-5 A) 4.74 B) 9.53 C) 9.13 D) 8.98 E) 9.25

ka * kb = 10^-14 ka = 10^-14/kb = 10^-14 / (1.8*10^-5) = 5.56*10^-10 pKa=-log(Ka)=-log(5.6*10^-10)=9.25 Molarity = moles/volume(liter) Moles = molarity * volume Moles of NH3 = 0.20M*(100/1000)L = 0.020 mol NH3 Moles of NH4Cl = 0.15 M * (250/1000)L = 0.0375 mol NH4Cl According to Henderson Hasselbalch Equation pH = pka + log[conjugate base]/[acid] pH = 9.25 log[NH3]/[Nh4+] = 9.25+log(0.020/0.0375) pH=8.976 = 8.98 D

What is n for the following equation in relating Kc to Kp? CH4(g) +H2O(g) <---> CO(g) + 3 H2(g) A) 2 B) 1 C) -1 D) -2 E) 3

n = Total # of products - Total # of reactants. = 4-2 = 2 A) 2

Calculate the pOH in a aqueous solution with a pH of 9.85 at 25C A) 5.15 B) 2.15 C) 4.15 D) 4.00

pOH = 14 - pH 14 - 9.85 C) 4.15

Place the following in order of increasing acid strength HBrO2 HBrO3 HBrO HBrO4 A) HBrO < HBrO2 < HBrO3 < HBrO4 B) HBrO2 < HBrO4 < HBrO < HBrO3 C) HBrO4 < HBrO2 < HBrO3 < HBrO D) HBrO2 < HBrO3 < HBrO4 < HBrO E) HBrO < HBrO4 < HBrO3 < HBrO2

the more O's in the BrOx ion, the easier it is to remove the H because the highly electronegative O's pull strongly on the shared electron A) HBrO < HBrO2 < HBrO3 < HBrO4