Part (a)
A chemist investigates the rate of reaction of four different calcium carbonate chips with dilute hydrochloric acid. Each chip has a different surface area.
They add each chip to 25 cm325\text{ cm}^325 cm3 of dilute hydrochloric acid and measure the time taken for the chip to completely react (dissolve). The table shows their results.
| Chip | Surface area of chip (cm2\text{cm}^2cm2) | Volume of chip (cm3\text{cm}^3cm3) | Surface area to volume ratio | Time taken to completely react (seconds) |
|---|---|---|---|---|
| A | 1.8 | 0.4 | 4.5 : 1 | 95 |
| B | 2.0 | 0.5 | 110 | |
| C | 1.5 | 0.2 | 7.5 : 1 | 62 |
| D | 2.4 | 0.3 | 8.0 : 1 |
Calculate the surface area to volume ratio of chip B.
Surface area to volume ratio = __________ : 1
Complete the sentence to describe the relationship between the surface area to volume ratio and the time taken to completely react.
As the surface area to volume ratio __________, the chip will take __________ time to completely react.
The chemist thinks that chip D will react the slowest in the acid. Explain why the chemist is incorrect.
Part (b)
The chemist performs paper chromatography on solutions of compounds extracted from the reaction mixtures.
The spots on the chromatogram are colourless. State one method the chemist could use to make the spots visible.
After using a method to see the spots, the chromatogram for Sample X is shown below.
Calculate the RfR_fRf value for the spot seen from Sample X.
RfR_fRf value = __________