A pipeline leak lasts 2.5 hours before it can be stopped. The mass flow rate of the leak is 1.5 kg/s. What is the quantity of the liquid spilled (in kg)?

• A. 9000 kg
• B. 13500 kg
• C. 18000 kg
• D. 22500 kg

Answer: (B)

Mass spilled equals the mass flow rate multiplied by the duration. Start by making the time consistent with the flow rate’s units. The leak lasts 2.5 hours, which is 2.5 × 3600 = 9000 seconds. With a flow rate of 1.5 kg per second, the total spilled mass is 1.5 × 9000 = 13,500 kg. Check the units: kg/s times s gives kg, as expected. Another way to see it is converting the flow rate to kilograms per hour (1.5 kg/s × 3600 s/hour = 5400 kg/hour) and multiplying by 2.5 hours to get the same result. The quantity spilled is 13,500 kg.