Please help with this three questions

5g of calcium carbonate takes 250s to react with hydrochloric acid completely. What is the average rate of the reaction?(Relative atomic masses: C=12.0,O=16.0,Ca=40.1 ) A. 0.16mols1 B. 0.020mols1 C. 2.0104mols1 D. 2.0105mols1 The following graph shows the volume of hydrogen gas produced against time. Which of the following statements about the above graph is INCORRECT? A. The reaction ends at the 8th minute. B. The average rate of the reaction is 7.25cm3min1. C. The instantaneous rate is the highest at the beginning. D. The instantaneous rate at t=2min is 21.0cm3min1. A conical flask that contains dilute sulphuric acid is placed on an electronic balance. Some sodium hydrogencarbonate powders are then added to the flask. Which of the following graphs represents the change in mass of the flask and its content against time? A. B. C. D