Question

Assuming equal concentrations, rank these solutions by pH. Highest pH (1) to lowest pH (5)

CaBr2 (aq) CH3NH3Br (aq) HCl (aq) RbOH (aq) K2CO3 (aq)

Answer 1

low pH -- > acidic

high pH -> basic

CaBr2 (aq) = Ca2+ + Br- ions will be neutral, pH = 7

CH3NH3Br (aq) --> slightly acidic sicne CH3NH3+ = CH3NH2 + H+ is formed, pH = 4-5 approx

HCl (aq) --> pH is low, since strong acid, pH = 1-3

RbOH (aq) --> pH is high, since strong base --> pH = 12-14

K2CO3 (aq) --> this is a weak base, 2K + CO3-2 --> CO3-2 + 2H2O <-> H2CO3 + OH-

then, pH = 9-11

therefore order

HCl < CH3NH3Br < CaBr2 < K2CO3 < RbOH