Pretest 3.3 Dissociation of Acids and Bases

New solutions

1. True or False?

a)      Only acidic solutions conduct electricity. _________

b)     Acid and base react together to produce an ionic compound and water. ________

c)      The sum of pH and pOH of any aqueous solution is always 14.0. _________

d)     The pH is a scale used to represent the concentration of hydrogen ion in a solution. ________

e)      The Kb(x) of solution X is 3.5x10-5 and Kb(y) of solution Y is 8.3x10-8. Then, solution Y is more basic than solution X. __________

f)       If dissociation of an acidic solution is endothermic, the Ka will decrease with increasing temperature. __________

 

2. Fill in the blanks.

[H+1] mol/L

[OH-1] mol/L

pH

pOH

Acidic or basic?

4.5x10-8

 

 

 

 

 

4.05x10-8

 

 

 

 

 

4.7

 

 

 

 

 

8.8

 

 

3. The acid dissociation constant for formic acid, HCO2H is 1.8x10-4.

a)      Write the equilibrium equation of formic acid dissociation.

b)     Calculate the pH of 0.050 M formic acid.  

 

4. The pH of hypobromous acid, HOBr(aq) is 4.85. What concentration of HOBr(aq) was used? (Ka=2.0x10-9)  

 

5. A solution of carbonic acid, H2CO3 dissociates into H+1(aq) and HCO3-1(aq).

a)      Write the equilibrium equation of carbonic acid dissociation.

b)     Calculate the Ka for 0.070 M solution of carbonic acid with pH of 3.76.

 

6. A 0.450 M solution of ethylamine, C2H5NH2 has pH of 12.2. Given:

C2H5NH2(aq) + H2O(l) = C2H5NH3+1(aq) + OH-1(aq)

a) What is the concentration of hydroxide ion?

b)     Calculate the Kb of the solution. 

 

7. The base dissociation constant for hydrazine, H2NNH2 is 3.0x10-6.

a)      Write the equilibrium equation when hydrazine dissociates in water.

b)     Calculate the pH of 1.50 M hydrazine solution.  

 

8. A 100.0 mL solution of ammonia, NH3 dissociates in water and the resulting pH is 11.48.  

a)      Write the equilibrium equation for ammonia.

b)     If the Kb of NH3(aq) is 1.8x10-5, what mass (in grams) of ammonia was present in the 100.0 mL solution?  

 

9. When 2.40 g of NH4NO3 (s) is dissolved in 25.0 mL of water at 250C, the temperature decreases to 19.270C. What is the molar enthalpy of NH4NO3?

 

10. a) At 300C and 101.3 KPa, what volume does 20.0 g of freon gas, CCl2F2, occupy?

b) What volume will 3.0 moles of freon gas occupy at STP?