Magnesium reacts with hydrochloric acid and 0.30 mol of hydrogen gas is collected in 2.5 minutes. What is the average rate of formation of hydrogen?

1. The average rate of formation of a product is the number of moles formed divided by the time. 2. Rates in chemistry are quoted per second, so the time must first be converted into seconds. 3. There are 60 seconds in a minute, so 2.5 minutes is 2.5 multiplied by 60. 4. That gives a reaction time of 150 seconds. 5. The rate is therefore 0.30 moles divided by 150 seconds. 6. That equals 0.0020 moles per second. 7. The 0.12 answer is the trap for dividing by 2.5 and leaving the time in minutes. 8. The 0.0050 answer divides by 60 seconds instead of 150, and the 0.0012 answer divides by 250 seconds by misreading 2.5 minutes. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Rate and Extent of Reaction_