please solve these four problems. thanks What is the concentration of Ag+ if pAg

Question

please solve these four problems. thanks

What is the concentration of Ag+ if pAg+ = 7.57? pAg+ = -log[Ag+] The Kb of NH3 is 1.80 times 10-5. What is the pH of a 0.650 M solution of NH4NO3? pKa = PH - log []/[] When 2.00 times 10-2 moles of nicotinic acid (a monoprotic acid) is dissolved in 350.0 mL of water, the pH is 3.05. What is the Ka of nicotinic acid? The term "proof" is a Spirits Industry term that is defined as twice the % by volume of pure ethanol (CH3CH2OH) in solution. Thus, a solution that is 95% (by VOLUME) ethanol is 190 proof (note for personal reference: 190 proof drinks can be lethal!). What is the MOLARITY of ethanol in a vermouth drink if the vermouth is 36 proof (no "rocks" or water added!)? Assume that the density of ethanol is 0.78 g/mL.

Explanation / Answer

ans1)

pAg+ = 7.57

so [Ag+] = 10^-7.57 = 2.69*10^-8 M

ans 2)

kb = 1.8*10^-5

kb*ka = 10^-14

Ka = 5.556*10^-10

NH4+ ---> NH3 + H+

0.65-x........x........x

ka = x^2/(0.65-x)

so x = 1.9*10^-5M = [H+]

pH = -log10[H+]

pH = 4.72

ans3)

concentration of nicotinic acid = 0.02/0.35 = 0.057M

nicotinic acid + H2O ---> H3O+ + conjuhate base

0.057-x..............................x...................x

ka= x*x/(0.057-x)

and pH = 3.05

[H+] = 10^-pH = 8.91*10^-4 M =x

so Ka = 1.41*10^-5

ans 4)

the vermouth is 36 proof,

so by volume is 18% EtOH.

density = m/V

0.78 g/ml = 780g/L

780 g/L * 0.18 = mass

140.4 grams = mass

Ethanol is CH3CH2OH

C: 2(12) = 24

H: 6 (1) = 6

O: 1(16) = 16

46 grams/mol

dividing we get

140.4 grams / 46 grams /mol = 3.05 moles

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