Question

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

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

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

Answer 1

Student B is correct. By conservation of mass the initial mass of water equals the total mass of the gases produced: 112 g H2 + 888 g O2 = 1000 g of H2O.