Chemistry MCQs

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Useful Information

R = 0.08206 atm L mol -1 K- 1  = 8.314 J mol -1 K -1

TK = TºC + 273.15 

Kw = 1.0 x  10-14

pH = pKa + log [A-]/[HA]

1. Macnic acid (HMac) has a pKa of 4.460.  Calculate the Kb of its conjugate base

   a. 1.76×10-11 

   b. 2.88×10-10 

   c. 1.74×10-11 

   d. 8.07×10-12 

   e. 7.08×10-12 

2. Which of the following ions will hydrolyze in water to give a basic solution?

   a. ClO4- 

   b. ClO2- 

   c. Na+ 

   d. NH4+ 

   e. NO3- 

3. Consider the following lists of acids: 

    List A: HBrO, HBrO2, HBrO3 

    List B: PH3, H2S, HCl 

The weakest acid of List A is  ______.  The weakest acid of List B is____

   a. HBrO, HCl 

   b. HBrO2, HCl 

   c. HBrO3, H2S 

   d. HBrO, PH3 

4. What is the molar solubility of Ca3(PO4)2 (Ksp = 2.10 x 10-33) in 0.609 M K3PO4?

   a. 3.52×10-10 M

   b. 2.42×10-10 M

   c. 5.94×10-12 M

   d. 3.31×10-10 M

   e. 5.12×10-10 M

5. A buffer consists of 0.414 M HCOOH (Ka = 1.8 x 10-5) and 0.749 M NaCOOH.  What is the pH of the buffer after the addition of 0.20 mol of HCl to 1.0 L of this buffer (Assume the volume doesn’t change)?

   a. 3.03 

   b. 3.61 

   c. 5.73 

   d. 4.70 

   e. 2.22 

6. Consider the titration of 31.1 ml of 0.300 M NH3 with 0.230 M HCl. What volume of HCl is required to reach the equivalence point?

   a. 54.6 mL

   b. 62.5 mL

   c. 40.6 mL

   d. 22.4 mL

   e. 53.0 mL

7. A certain chemical reaction has ΔHro < 0 and a ΔSro > 0. Which statement is correct?

   a. The reaction is only spontaneous at low temperatures 

   b. The reaction is only spontaneous at high temperatures 

   c. The reaction is spontaneous at all temperatures 

   d. The reaction is never spontaneous 

8. A weak acid indicator has a Ka = 1.3 x 10-3.  It changes color from pink (acidic color) to orange (base color) around pH of ___. Therefore at pH of 7.00 this indicator is  _____

   a. 3, pink 

   b. 5, pink 

   c. 3, orange 

   d. 5, orange 

   e. 1, pink 

9. One liter of each of the following solutions are mixed. After mixing, which one is a buffer?

   a. 0.4 M HF and 0.4 M KOH 

   b. 0.75 M NH3 and 0.5 M HCl 

   c. 0.4 M HCN and 0.6 M NaOH 

   d. 0.2 M HCl and 0.1 M KOH 

10. When 1 liter volumes of the below solutions are mixed, which will result in the precipitation of PbCl2 ( Ksp = 1.7 x 10-5)

   a. 0.04 M Pb(NO3)2 and 0.08 M KCl 

   b. 0.001 M Pb(NO3)2 and 0.05 M KCl 

   c. 0.002 M Pb(NO3)2 and 0.02 M KCl 

   d. 0.002 M Pb(NO3)2 and 0.02 M KCl 

   e. 0.01 M Pb(NO3)2 and 0.005 M KCl 

11. In which of the following is BaCO3 least soluble?

   a. 0.1 M Na2CO3 

   b. 0.05 M BaNO3 

   c. 0.01 M HCl 

   d. 0.1 M KI 

12. A solution is 3.82 x 10-3 M in both Ca2+ and Sr2+. Solid K2SO4 is added to precipitate the sulfates. What concentration of sulfate is need to precipitate as much of the Sr2+ without precipitating any of the Ca2+ (Ksp(CaSO4) = 2.40 x 10-5, and Ksp(SrSO4) = 2.80 x 10-7)?

   a. 7.41×10-3 M

   b. 3.17×10-3 M

   c. 7.05×10-3 M

   d. 6.28×10-3 M

   e. 2.21×10-3 M

13. A buffer solution is 0.824 M in CH3NH2 (Kb = 4.4 x 10-4) and 0.843 M in CH3NH3Cl.  What is the pH of this buffer?

   a. 12.3 

   b. 8.42 

   c. 7.57 

   d. 12.2 

   e. 10.6 

14. Consider the titration of 50.0 ml of 0.262 M HF (Ka = 1.3 x 10-5) with 0.200 M NaOH. What is the pH of the solution after the addition of 17.5 ml of the NaOH?

   a. 2.30 

   b. 3.33 

   c. 2.60 

   d. 4.45 

   e. 3.20 

15. Consider the following reaction 

   2 A  + 3 B –> 3 C 

If ΔGfo of A, B and C are 123 kJ/mol, -242 kJ/mol and 225 kJ/mol respectively, calculate ΔGro for the reaction

   a. 572 kJ/mol

   b. 720. kJ/mol

   c. 493 kJ/mol

   d. 1.16×103 kJ/mol

   e. 520. kJ/mol

16.  Which statement is correct?

   a. During a spontaneous process the entropy change is zero  

   b. All Bronsted-Lowry acids are also Lewis acids 

   c. During a spontaneous process the Gibbs energy increases 

   d. Salts of weak bases are basic 

   e. Silver chloride is completely insoluble 

17. What is the common ion when a solution of HCl is mixed with a solution of NaCl

   a. H3O+ 

   b. Na+ 

   c. Cl- 

   d. OH- 

18. If the base dissociation constant of ammonia is 1.8 x 10-5, what is the pH of a 0.212 M solution of NH4I?

   a. 5.91 

   b. 4.96 

   c. 3.76 

   d. 2.01 

   e. 3.36 

19. Which of the following salts would you expect to be neutral?

   a. AlCl3 

   b. KF 

   c. NH4Br 

   d. Ca(NO2)2 

   e. KClO4 

20. Which of the following is most likley to act as a Lewis base?

   a. Cl- 

   b. Ag+ 

   c. H+ 

   d. BF3 

21. Given the following weak acids and their associated pKa 

     HMac, pKa = 4.1,       HTern, pKa = 3.0,

     HBrun, pKa = 5.5,      HTharn, pKa = 7.33. 

Which one of the below would be the best choice to prepare a buffer with pH =4.3 ?

   a. ternic acid (HTern) and sodium ternate 

   b. brunic acid (HBrun) and sodium brunate 

   c. macnic acid (HMac) and sodium macnate 

   d. tharnic acid (HTharn) and sodium tharnate