42 !

during a physical science lab investigating chemical reactions, several students placed a 30g antacid tablet in a 30g zip-lock bag. they recorded the masses of the tablet, and the bag. then they added 50 grams of water and quickly sealed the bag. the tablet began to fizz and soon disappeared. the bag was filled with gas. if the mass of the liquid after the reaction is completed is still 50 grams, how much gas is produced? a) 30 grams b) 50 grams c) 80 grams d) 90 grams

A) 30 g

Explanation: The reactants here are antacid tablet and water which are 30 g and 50 g respectively. Thus the total mass of the reactants is 30 g.

The products formed are in two states, one is in liquid state which weighs 50 g and the other is gas.

According to the law of conservation of mass, the mass of the products would always be the same as the mass of the reactants. Thus the mass of the products should also be 80 g. As the mass of liquid product is 50 g , the mass of the gas produced should be (80 g - 50 g) = 30 g.