1. Questions 1-2 refer to the following information. Hydrogen Gas Water Test Tub

Question

1. Questions 1-2 refer to the following information. Hydrogen Gas Water Test Tube Calcium Calcium metal will react with water to generate hydrogen gas. A setup for a lab collection of the gas in this reaction is shown in the diagram above. The equation for the balanced reaction is given below. Ca(s) + 2 H2O(l) Ca(OH)2(aq) + H2(g) AH°=-414 kJ/mol A student submerged a 0.20 g lump of calcium, Ca(s), in a test tube containing 20. mL of water and measured the hydrogen gas production over time using the setup shown above. The student notes that the rate of production of hydrogen gas increases as the reaction progresses. Which of the following best explains the increased rate of reaction? (A) Since water is consumed in the reaction, the remaining water's concentration increases during the reaction. (B) The temperature of the water in the test tube increases during the reaction because the reaction is exothermic which increases the rate of the reaction. (C) This is a second order reaction whose rate constant increases as the amount of reactants decreases. (D) The calcium lump gets smaller during the reaction allowing the water to more easily make contact with the metal, increasing the rate of the reaction. 2. The student repeats the experiment this time with 0.20 g of granular calcium and 20. mL of water. The reaction goes to completion in half the time of that of the calcium lump. Which of the following statements best explains the difference in the time for the reaction? (A) The specific heat capacity of granular calcium is lower than the metal lump, so the reaction rate of the production of hydrogen will increase. (B) The granular calcium produces less hydrogen than the solid metal lump so the reaction goes to completion sooner. (C) The granular calcium has a larger surface area to react with the water so the rate of the reaction increases. (D) The granular calcium is more concentrated than the lump form which increases the rate of the reaction.

Explanation / Answer

1.option B is correct

Reason

This is an example of exothermic reaction(since the delta H vale is negative) so by increasing the temperature the reaction goes forward ( according to le chatlier principle) . Thereby increasing the rate of hydrogen production.

2.option c is correct

Reason

In granular calcium the surface area is more and because of more surface area calcium can react with water to give hydrogen gas.

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