Question

In the equation below, 46 grams of sodium (Na) reacted with 36 grams of water (H2O).

If 2 grams of hydrogen gas (H2) is produced by this reaction, what is the mass of sodium hydroxide (NaOH) produced?

A.10 grams

B.44 grams

C.80 grams

D.82 grams

Answer 1

The correct answer is: C.80 grams  

2Na+2H2O --->2NaOH+H2

Moles of sodium (Na) = n

n = m / M

n = 46g / 23g/mol = 2 moles

Moles of water (H2O) = n1

n1 = 36g / 18g/mol = 2 moles

Mass of NaOH = m1

m1 = 2moles * 39,9g / mol = about 80grams

Answer 2

Answer: Option (C) is the correct answer.

Explanation:

According to law of conservation of mass, mass can neither be created nor it can be destroyed. It can only be changed from one form to another.

This means that in a chemical reaction, the total mass of reactants will always be equal to the total mass of products.

As it is given that, 46 grams of sodium (Na) reacted with 36 grams of water (H2O). As both Na and $H_{2}O$ are the reactants.

Since, $H_{2}$ is the product and its mass is given as 2 g. Therefore, calculate the mass of NaOH formed as follows.

                     Total mass of reactants = Total mass of products

                                46 g + 36 g = mass of NaOH + 2 g

                             mass of NaOH = 82 g - 2 g

                                                       = 80 g

Thus, we can conclude that mass of sodium hydroxide (NaOH) produced is 80 grams.