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

Question

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In a lab, 96g of hydrogen gas and 404g of oxygen gas were collected. Student A says that the starting amount of water cannot be determined, but Student B says that the water must have been 500g. Who is correct?

(1 point)
Responses

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

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 was 2000g because the equation shows 2H2O
.
Neither are correct. It was 2000g because the equation shows 2 cap h sub 2 cap o.

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

Answer 1

To determine the starting amount of water based on the reaction and the masses of hydrogen and oxygen collected, we can use the law of conservation of mass. According to this law, the mass of the reactants should equal the mass of the products.

From the balanced equation: \[ 2H_2O \rightarrow 2H_2 + O_2 \]

This indicates that 2 moles of water produce 2 moles of hydrogen and 1 mole of oxygen.

1. Calculate the molar masses:

   • Molar mass of \( H_2 \) (hydrogen) = 2 g/mol
   • Molar mass of \( O_2 \) (oxygen) = 32 g/mol

2. Calculate the total mass of gases collected:

   • Mass of hydrogen collected = 96 g
   • Mass of oxygen collected = 404 g
   • Total mass of gases = 96 g + 404 g = 500 g

3. The law of conservation of mass states that the mass of the starting substances (water) should equal the mass of the products (hydrogen and oxygen):

   • Mass of water = Mass of hydrogen + Mass of oxygen = 500 g

In this case, Student B is correct because the law of conservation of matter supports that the total mass of water that was split should equal the total mass of the gases collected.

So, the correct answer is: Student B, because the law of conservation of matter.