Calculate the maximum mass of sodium bromide that could be produced by the chemical reaction. Be sure your answer has the correct number of significant digits.

Question

Aqueous hydrobromic acid HBr

 will react with solid sodium hydroxide NaOH

 to produce aqueous sodium bromide NaBr

 and liquid water H2O

.Suppose 3.24 g of hydrobromic acid is mixed with 2.9 g of sodium hydroxide. Calculate the maximum mass of sodium bromide that could be produced by the chemical reaction. Be sure your answer has the correct number of significant digits. 

Answer 1

HBr(aq) + NaOH(aq) ==> NaBr(aq) + H2O(l) ... balanced equation

Because we are given the amounts of BOTH reactants, we must first determine which reactant is limiting. One way to do this is to divide the moles of each reactant by the corresponding coefficient in the balanced equation. Whichever result is less will identify the limiting reactant.

For HBr: 3.24 g x 1 mol HBr / 80.9 g = 0.0400 moles HBr

For NaOH: 2.9 g x 1 mol NaOH / 40 g = 0.0725 mols NaOH

Since both have coefficients of 1, the HBr is the limiting reactant.

Now, use the moles of HBr to calculate the mass of NaBr:

0.0400 mols HBr x 1 mol NaBr / mol HBr x 103 g / mol NaBr = 4.1 g NaBr (2 sig. figs.)