Of the compounds below, a 0.1 M aqueous solution of will have the lowest pH. KCN
ID: 1021830 • Letter: O
Question
Of the compounds below, a 0.1 M aqueous solution of will have the lowest pH. KCN, K_a of HCN = 4.0*10^-10 NH_4NO_3, K_b pf NH_3 = 1.8*10^-5 NaOAc, k_a of HOAc = 1.8*10^-5 NaClO, K_a of HClO = 3.2*10^-8 NaHS, k_b of HS* = 1.8*10^-7 A Bronsted - Lowry acid is defined as a substance that increases [H^+] when placed in H_2O decreases [H^+] when placed in H_2O increases [OH^-] when placed in H_2O acts as a proton acceptor acts as a proton donor The pH of 0.01 M solution of Ca(OH)_2. 1.67 12.3 10.2 2 0.01 A 0.1 M solution of has a pH of 7.0. Na_2S NaNO_3 NH_4Cl NaFExplanation / Answer
1. CN- + H2O ----------> HCN + H2O
I 0.1 0 0
C -x +x +x
E 0.1-x +x +x
Kb = Kw/Ka
= 1*10-14/4*10-10 = 2.5*10-5
Kb = [HCN][OH-]/[CN-]
2.5*10-5 = x*x/0.1-x
2.5*10-5 *(0.1-x) = x2
x= 0.00156
[OH-] =x = 0.00156M
POH = -log[OH-]
= -log0.00156
= 2.8068
PH = 14-POH
= 14-2.8068 = 11.1932
A) KCN , Ka of HCN = 4*10-10
2. proton donor is called Bronsted lowery acid.
E) act as proton donor
3. Ca(OH)2 ---------> Ca+2 + 2OH-
0.01 2*0.01
[OH-] = 2*[Ca(OH)2]
= 2*0.01M = 0.02M
POH = -log[OH-]
=- log0.02
= 1.6989
PH = 14-POH
= 14-1.6989
= 12.3011
C) 12.2
4)
B)KF
it is a salt of strong acid and strong abase. so salt solution is neutral . PH -7
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