The reaction for the auto-ionization of water is: H20 (l) + H2O (l) = H3O+ (aq)

Question

The reaction for the auto-ionization of water is: H20 (l) + H2O (l) = H3O+ (aq) + OH- (aq). The reverse reaction dominates the forward reaction. This means that a sample of water will contain (pick one) a) about one-half ions and one-half malecules b) mostly H3O+ and OH- ions, and very few H2O molecules c) mostly H2O molecules, and very few ions. 1) 1.0 x 10-3 M solution of HCl: [H+] = ______M, pH = _______; 0.200 M solution of HNO3: [ H+]= ______M, pH = _________; 1.0M solution of HClO4: [H+] = __________M, pH = _______________

Explanation / Answer

The reaction for the auto-ionization of water is: H20 (l) + H2O (l) = H3O+ (aq) + OH- (aq). The reverse reaction dominates the forward reaction. This means that a sample of water will contain mostly H2O molecules, and very few ions.

1. 1.0 x 10-3 M solution of HCl: [H+] = 1.0 x 10-3 M, pH = 3

HCl is undergoes complete ionisation, its [H+] = 1 X 10-3M so its pH = -log[H+] = -log 1 x 10-3

= - log 10-3 = 3 log 10 =3

2. 0.200 M solution of HNO3: [H+] = _____0.200_M, pH = 0.699

HNO3 is undergoes complete ionisation, its [H+] = 0.2 M, so its pH = -log[H+] = -log 0.2

=-log 2 X 10-1 = - (log2 + log 10-1)

=-0.3010 + 1

=0.699

3. 1.0M solution of HClO4: [H+] = __1 M________M, pH = 0

HClO4 is undergoes complete ionisation, its [H+] = 1 M, so its pH = -log[H+] = -log 1 = 0

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