Question

For a 0.0309 M aqueous solution of cyanic acid, HCNO (Ka = 3.5*10-4), determine the following.

What are the major and minor species present? Include phase. What is the major species (other than water)? Edit What is the minor species (other than H3O+ and OH-)? Edit LINK TO TEXT

What is the concentration of the minor species in the solution? M The number of significant digits is set to 1; the tolerance is +/-4% LINK TO TEXT

What is the concentration of the major species in the solution? M The number of significant digits is set to 3; the tolerance is +/-4% LINK TO TEXT

What is the concentration of H3O+ in the solution? M The number of significant digits is set to 2; the tolerance is +/-4% LINK TO TEXT

What is the concentration of OH- in the solution? M The number of significant digits is set to 2; the tolerance is +/-4% LINK TO TEXT

Find the pH. The number of significant digits is set to 2; the tolerance is +/-4%

Answer 1

What is the major species? : HCNO (aq)

What is the minor species? : CNO- (aq)

What is the concentration of the minor species in the solution? : 3 x 10^-3 M

What is the concentration of the major species in the solution? : 0.0278 M

What is the concentration of H₃O⁺ in the solution? : 3.1 x 10^-3 M

What is the concentration of OH^- in the solution? : 3.2 x 10^-12 M

Find the pH : 2.5

Explanation

Given : initial concentration of HCNO = 0.0309 M

Ka = 3.5 x 10^-4

ICE table	HCNO (aq)	H2O (l)	$\rightleftharpoons$	CNO- (aq)	H3O+ (aq)
Initial conc.	0.0309 M	-		0	0
Change	-x	-		+x	+x
Equilibrium conc.	0.0309 M - x	-		+x	+x

Ka = [CNO-]eq[H3O+]eq / [HCNO]eq

3.5 x 10^-4 = [(x) * (x)] / (0.0309 M - x)

Solving for x, x = 3.12 x 10^-3 M

[H3O+] = x = 3.12 x 10^-3 M

pH = -log[H3O+]

pH = -log(3.12 x 10^-3 M)

pH = 2.51