Under certain conditions, water can be separated into oxygen and hydrogen gases according to the equation 2H2O → 2H2 + O2.

In a lab, 112g of hydrogen gas and 888g of oxygen gas were collected. Student A says that the amount of water to start cannot be determined, but Student B says that the water must have been 1000g. Who is correct?

(1 point)
Responses

Student A, because the water was not measured to start with.
Student A, because the water was not measured to start with.

Neither are correct. It would have been 1112g, because there are 2 H2 to 1 O2.
Neither are correct. It would have been 1112g, because there are 2 H 2 to 1 O 2 .

Student B, because of the law of conservation of matter.
Student B, because of the law of conservation of matter.

Neither are correct. It was 2000g because the equation shows 2H2O.

The correct answer is Student B, because of the law of conservation of matter. According to this law, the total mass of reactants must equal the total mass of products in a chemical reaction. Since the total mass of hydrogen gas and oxygen gas collected is 1000g, it must have come from 1000g of water.