If 5g of Iron filling was reacted with excess dilute H 2 SO 4 to evolve hydrogen gas, which came to completion…

1. Analyze the question

We are given the mass of a reactant (Iron) consumed in a chemical reaction and the time taken for the reaction to complete. We need to calculate the rate of reaction specifically in the unit of grams per hour (g/hr).

2. Explain the concept

The rate of reaction is defined as the change in the amount of a reactant or product per unit time. The formula is:

To get the answer in g/hr, we must ensure the mass is in grams (which it is: 5g) and the time is converted from minutes to hours.

3. Show the solution

• Step 1: Identify the given values. • Mass of Iron = 5g • Time = 10 minutes

• Step 2: Convert time from minutes to hours. Since there are 60 minutes in 1 hour: $$\text{Time in hours} = \frac{10 \text{ minutes}}{60 \text{ minutes/hour}} = \frac{1}{6} \text{ hours}$$

• Step 3: Calculate the rate. $$\text{Rate} = \frac{\text{Mass}}{\text{Time}}$$ $$\text{Rate} = \frac{5 \text{ g}}{1/6 \text{ hr}}$$ $$\text{Rate} = 5 \times 6 = 30 \text{ g/hr}$$

4. Identify the answer

Comparing our result to the given options: A. 5 B. 30 C. 20 D. 10

The calculated value matches option B.

5. Tip

Always check the units requested in the question! JAMB examiners often provide time in minutes or seconds but ask for the rate in hours to test if you remember to perform the unit conversion. Don't let a simple unit oversight cost you marks.