Question

the chemical equation for the reaction of sodium metal with water is 2na(s) + h₂o(l) → h₂(g) + 2naoh(aq). the reaction of 23 g of sodium with 9 g of water produces 1 g of hydrogen gas. what mass of sodium hydroxide is produced?
o a) 30 g
o b) 32 g
o c) 41 g
o d) 43 g

Explanation:

Step1: Apply law of conservation of mass

According to the law of conservation of mass, the total mass of reactants equals the total mass of products in a chemical - reaction.
The mass of reactants is the sum of the mass of sodium and water, $m_{reactants}=23\ g + 9\ g=32\ g$.

Step2: Calculate mass of sodium hydroxide

The mass of products is the sum of the mass of hydrogen gas and sodium hydroxide. Let the mass of sodium hydroxide be $m_{NaOH}$.
We know that $m_{reactants}=m_{products}$, so $32\ g=m_{H_2}+m_{NaOH}$.
Given $m_{H_2} = 1\ g$, then $m_{NaOH}=32\ g - 1\ g=31\ g$.

Answer:

C. 31 g