Ms. block's students are studying chemical reactions as well as the law of conservation of matter. a classic reaction occurs when a metal is added to hydrochloric acid. miguel and kai are about to add 30g of hydrochloric acid (hcl) to 30g of magnesium (mg) in a large test tube. how could you adapt the boys experimental design so they would definitely be testing the law of conservation of matter? a) the boys could use less hydrochloric acid to produce less gas bubbles. b) the boys should use a container, such as a flask, that is larger than a test tube. c) the boys could cover the end of the test tube with a balloon to capture the escaping gas. d) one of the boys could place a hand over the end of the test tube to create a closed system.

The answer is; C

Conservation of matter in a reaction means that the mass of matter in the products is equal to the mass of the reactants. Energy/matter cannot be created or destroyed but converted from one form to another.

An expanding balloon with the increased evolution of gas is a good visible practical sign in the experiment on the conservation of matter in the reaction. As the magnesium disappears with an increased input of hydrochloric acid, the balloon gets bigger showing that more hydrogen is evolved from the reaction;

2HCL + Mg  MgCl2 + H2  

the correct answer is b. a strong acid completely dissociates to its ions when dissolved in water. completely dissociates to and ions. a is incorrect because does not fully ionize to and ions and some remain as the compound . c and d are incorrect because, and do not fall into the category of bronsted lowry acids. a bronsted lowry acid is a proton donor and since both molecules do not have a proton to donate they are not bronsted lowry acids. likewise,   if we use the lewis acid definition, they cannot be acids. a lewis acid is an electron pair acceptor. both and have a complete octet so can not accept any electrons which disqualifies them as acids.