A chemist investigates how fast four different sodium hydrogencarbonate tablets dissolve in a dilute citric acid solution. Each tablet has a different surface area. They add each tablet to 50 cm3 of dilute citric acid and measure the time taken for it to completely dissolve. The table shows their results:
| Tablet | Surface area of tablet (cm2\text{cm}^2cm2) | Volume of tablet (cm3\text{cm}^3cm3) | Surface area to volume ratio | Time taken to dissolve (seconds) |
|---|---|---|---|---|
| W | 4.5 | 0.5 | 9.0 : 1 | 85 |
| X | 2.4 | 0.2 | 12.0 : 1 | 62 |
| Y | 1.6 | 0.2 | 96 | |
| Z | 5.4 | 0.3 | 18.0 : 1 |
Calculate the surface area to volume ratio of tablet Y.
Complete the sentence to describe the relationship between the surface area to volume ratio and the time taken to dissolve: "As the surface area to volume ratio increases, the tablet will take ______________ time to dissolve."
The chemist thinks that tablet Z will take the longest time to dissolve (dissolve slowest) in the acid. Explain why the chemist is incorrect.
The chemist performs thin-layer chromatography (TLC) on a solution containing an indicator from tablet W. The spots on the resulting chromatogram are colourless. State what the chemist could use to see the spots.
After using a technique to visualize the spots, the chromatogram for Tablet W is shown below:
Calculate the Rf R_f\,Rf value for the spot seen from Tablet W. Show your working.