Question 19N.3.sl.TZ0.1b(i)
| Date | November 2019 | Marks available | [Maximum mark: 3] | Reference code | 19N.3.sl.TZ0.1b(i) |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Determine, Show | Question number | b(i) | Adapted from | N/A |
A student investigated how the type of acid in acid deposition affects limestone, a building material mainly composed of calcium carbonate.
The student monitored the mass of six similarly sized pieces of limestone. Three were placed in beakers containing 200.0 cm3 of 0.100 mol dm−3 nitric acid, HNO3 (aq), and the other three in 200.0 cm3 of 0.100 mol dm−3 sulfuric acid, H2SO4 (aq).
The limestone was removed from the acid, washed, dried with a paper towel and weighed every day at the same time and then replaced in the beakers.
The student plotted the mass of one of the pieces of limestone placed in nitric acid against time.
[Source: © International Baccalaureate Organization 2019]
Determine the initial rate of reaction of limestone with nitric acid from the graph.
Show your working on the graph and include the units of the initial rate.
[3]
tangent drawn at time zero ✔
g day−1 ✔
0.16 ✔
NOTE: Accept other reasonable units for initial rate eg, mol dm−3 s−1, mol dm−3 min−1, g s−1 OR g min−1.
M3 can only be awarded if the value corresponds to the correct unit given in M2.
Accept values for the initial rate for M3 in the range: 0.13 − 0.20 g day−1 OR 1.5 × 10−6 g s−1 − 2.3 × 10−6 g s−1 OR 7.5 × 10−8 − 1.2 × 10−7 mol dm−3 s−1 OR 4.5 × 10−6 − 6.9 × 10−6 mol dm−3 min−1 OR 9.0 × 10−5 − 1.4 × 10−4 g min−1 OR a range based on any other reasonable unit for rate.
Ignore any negative rate value.
Award [2 max] for answers such as 0.12/0.11 g day−1, incorrectly obtained by using the first two points on the graph (the average rate between t = 0 and 1 day).
Award [1 max] for correctly calculating any other average rate.
