For 0.51 M HCN (Ka=6.2 x 10-10), mark the majorand minor species found in the so

Question

For 0.51 M HCN (Ka=6.2 x 10-10), mark the majorand minor species found in the solution. H+ HCN CN- H2O OH- Now calculate the pH of 0.51 M HCN solution. (Ka=6.2 x 10^-10)

Explanation / Answer

i'm assuming your'e in chem 1a as ucsc? me too! don't understand how to do mass and charge balances at all, but here's how you do the problem: HF --> H+ + F- I .6------- 0 ------1 C -x ------+x-----+x E .6-x----- x -----1+x so, 7.2E-4 = (x)(1)/(.6) you can ignore the x's in equilibrium concentrations of HF and F- since Ka is small. Thus, x=4.32E-4 -log(4.32E-4)=pH=3.36 (A) HF + NaOH --> H2O + NaF I .6 ------ .1 -------------------1 C -.1------ -.1 ---------------- +.1 E .5 ------- 0 ------------------1.1 pH=pKa+log(base/acid) pH= -log(7.2E-4) + log(1.1/.5) pH=3.49 (B) KF + HCl --> HF + KCl I 1------ .2 ------ .6 C -.2---- -.2 ----- +.2 E .8 ------ 0 ------- .8 Kw/Ka=Kb=1.39E-11 pOH=pKb + log(acid/base)=10.9+log(.8/.8) pOH=10.9 14-pOH=pH=3.14

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