A student investigates the rate of reaction between magnesium and hydrochloric acid. The reaction gives off hydrogen gas. The student wants to investigate how changing the concentration of the hydrochloric acid affects the rate of reaction. Look at her plan. First experiment I will put 0.5 g of magnesium ribbon into the flask. I will add 50 cm3 of hydrochloric acid. I will measure how fast the gas is given off. Second experiment I will put another 0.5 g of magnesium ribbon into the flask. I will add 100 cm3 of the same hydrochloric acid. I will measure how fast the gas is given off. Another student thinks that the plan will not work and he does not understand exactly what he has to do. Suggest how the plan for this investigation can be improved.