| Date | May 2015 | Marks available | 1 | Reference code | 15M.1.hl.TZ1.26 |
| Level | HL | Paper | 1 | Time zone | TZ1 |
| Command term | Question number | 26 | Adapted from | N/A |
Question
The forward reaction of this equilibrium is endothermic.
\[{{\text{H}}_{\text{2}}}{\text{O(l)}} \rightleftharpoons {{\text{H}}^{\text{ + }}}{\text{(aq)}} + {\text{O}}{{\text{H}}^ - }{\text{(aq) }} {K_w} = 1.0 \times {10^{ - 14}}{\text{ at 25 }}^\circ {\text{C}}\]
What is correct about water at 50 °C?
A. \({\text{[}}{{\text{H}}^{\text{ + }}}{\text{]}} > {\text{[O}}{{\text{H}}^ - }{\text{]}}\)
B. \({\text{[}}{{\text{H}}^ + }{\text{]}} < {\text{[O}}{{\text{H}}^ - }{\text{]}}\)
C. \({\text{pH}} < {\text{7.0}}\)
D. \({\text{pH}} = {\text{7.0}}\)
Markscheme
C
Examiners report
[N/A]
Syllabus sections
Additional higher level (AHL) » Topic 18: Acids and bases » 18.2 Calculations involving acids and bases
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