Question 17N.3.sl.TZ0.b
| Date | November 2017 | Marks available | [Maximum mark: 2] | Reference code | 17N.3.sl.TZ0.b |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Suggest | Question number | b | Adapted from | N/A |
Antacids react with hydrochloric acid in the stomach to relieve indigestion. A student investigated different brands of antacid to see which caused the largest increase in pH in a given time. She added the antacids to hydrochloric acid, and recorded the change in pH over five minutes.
Suggest two variables, besides the time of reaction, which the student should have controlled in the experiment to ensure a fair comparison of the antacids.
[2]
Any two from:
volume «of HCl»
concentration «of HCl»/[HCl]
temperature «of HCl»
mass of antacid/tablets
size of antacid particles/tablets
OR
surface area of antacid «particles»/tablets
Accept “number of tablets/different doses”.
Do not accept “same pH meter” OR “initial pH” OR “concentration of antacid/[antacid]”.
A variable must be given so do not accept answers such as “stirring”, “whether tablets are whole or crushed” etc.
[Max 2 Marks]
