1.- Calculate the value of the equilibrium constant for the following reactions:
ID: 800783 • Letter: 1
Question
1.- Calculate the value of the equilibrium constant for the following reactions:
a) NH3 +H3O+<-->NH4+ + H2O
b) NO2^- + H3O+ <-->HNO2 + H2O
c) NH4^+ + OH- <--> NH3 +H2O
d) HNO2 + OH- <--> NO2^- + H2O
e) Classify the reaction in a through d.
f) In solving problems, for the reactions a through d, should the final concentration for these reactions be found by treating the reactions as equilibrium or as stoichiometry problems?
2.- Calculate the pH of the following aqueous solutions:
a)1.5*10^-5M HCl
b)1.0 mL of sample a in 0.50 L of water.
3.- What is the ionization of a solution of 0.20M benzoic acid, C6H5COOH (Ka=9.6*10^-5)?
Would a 0.02M benzoic acid solution have a higher or lower % ionization (hint: use Le Chatelier's principle.) Would it have a higher or lower pH?
4.- Calculate the pH of a 0.0010 solution of HB, a hypothetical acid with Ka= 9.6*10^-5. ((use the method of successive approximations, if necessary.) What molarity of acetic acid would have the same pH as this HB solution?
Explanation / Answer
Net Ionic Equation:
NH4 + H2O -> NH3 + H3O
kb[NH3]=1.8x10^-5 (should be on a table you have)
NH4 + H2O -> NH3 + H3O
0.65 0 0
-x +x +x
0.65-x x x
kb=([NH3][H30])/[NH4]
1.8X10^(-5) = (x^2)/0.65-x
kw=(ka)(kb)
kw=1.0x10^(-14)
solve for x and you should have [H3O].
plug in x to 0.65-x and you should have [NH4].
plug in values for 100x[H3O]/[NH4].
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