What is rate of reaction?

The molecular formula for caffeine is cshion402. which of the following elements is not found in caffeine?

7. what temperature is need to just dissolve 50 g of nh4cl in 75 g of water? '

Alidded glass container is filled with a colored gas. after a period of time, it is observed that the gas is uniformly spread throughout the box and that the movement has slowed considerably. next, a warm iron plate is carefully placed under the box. why is there resumed movement of the gas in the container?