Question #146675
Calculate the pH (give your answers to 2.d.p) of the following solution dilutions.
(a) 50 cm3 of 1.00 mol dm–3 hydrochloric acid is added to 200 cm3 of water.
(b) 100 cm3 of 1.00 mol dm–3 Ba(OH)2 is added to 400 cm3 of water at 298 K
Expert's answer
a) C1V1=C2V2
C1=1.00moldm-3
V1= 50 cm3
C2=?
V2= (50+200) cm3
=250 cm3
1 ×50= 250 C2
C2=50/250
=0.2M
[H+] = 0.2M
pH=-log (0.2)
=0.6990
=0.70 (2dp)
b) C1=1. 00moldm-3
V1=100 cm3
C2=?
V2= (100+400) cm3
=500 cm3
100×1=500 C2
C2= 100/500
C2=0.2MBa(OH)2
Ba(OH)2(aq) =Ba2+(aq) +2OH-(aq)
[OH-]= 2×0.2= 0.4M
pOH=-log[OH-]
=-log [0.4]
=0.3979
pH=14-0.3979
=13.6021
=13.60 (2dp)
