Question

In a chemical reaction, molecules of hydrogen gas (H2) react with molecules of oxygen gas (O2) in a sealed reaction chamber to produce water (H2O). This occurs through the following chemical equation. 2H2 + O2 → 2H2O What is conserved as the reaction occurs in the reaction chamber? A. temperature B. mass C. flammability D. molecule size

Answer 1

Answer:

Option (B) is correct.

Explanation:

Given that the molecules of hydrogen gas ($H_2$) react with molecules of oxygen gas ($O_2$) in a sealed reaction chamber to produce water ($H_2O$).

The governing equation for the reaction is

$2H_2 +O_2 \rightarrow 2H_2O$

From the given, the only fact that can be observed that 2 moles of $H_2$ and 1 mole of $O_2$ reacts to produce 2 moles of $H_2O$.

As the mass of 1 mole of $H_2 = 2$ grams ... (i)

The mass of 1 mole of $O_2 = 32$ grams ...(ii)

The mass of 1 mole of $H_2O = 18$ grams (iii)

Now, the mass of the reactant = Mass of 2 moles of $H_2$ + mass 1 mole of  $O_2$

$= 2 \times 2 + 32$  [ using equations (i) and (ii)]

$=4+32 = 36$ grams.

Mass of the product = Mass of 2 moles of $H_2O$

$=2\times 18$ [ using equations (iii)]

=36 grams

As the mass of reactants = mass of the product.

So, mass is conserved.

Hence, option (B) is correct.