chemistry question

Question

Aqueous hydrobromic acid HBr

 will react with solid sodium hydroxide NaOH

 to produce aqueous sodium bromide NaBr

 and liquid water H2O

.Suppose 75.2 g of hydrobromic acid is mixed with 65. g of sodium hydroxide. Calculate the maximum mass of sodium bromide that could be produced by the chemical reaction. Round your answer to 3

 significant digits. 

Answer 1

Hi Alya A.!

This is a limiting reagent question involving an acid-base neutralization. One way to solve problems such as these is to use stoichiometry on two separate calculations, one for each starting material. Then determining which reagent is limiting owing to the theoretical yield. Let's have a look:

Step 1: Balance Equation

The first step in many chemistry questions is ensuring you have a balanced equation.

HBr_(aq) + NaOH_(aq) -------> NaBr_(aq) + H₂O_(l)

Step 2a: Stoichiometry with Hydrobromic Acid as the Starting Material

(75.2g HBr)(1 mol HBr/80.912g HBr)(1 mol NaBr/1 mol HBr)(102.89g NaBr/1 mol NaBr)

mass = 95.6g NaBr

Step 2b: Stoichiometry with Sodium Hydroxide as the Starting Material

(65.g NaOH)(1 mol NaOH/39.9972g NaOH)(1 mol NaBr/1 mol NaOH)(102.89g NaBr/1 mol NaBr)

mass = 167.2g NaBr = 1.7x10²g NaBr

Step 3: Limiting Reagent

Our calculations demonstrate that we have enough sodium hydroxide to produce 170g of sodium bromide. However, we have only enough hydrobromic acid to produce 95.6g of sodium bromide. We have an insufficient amount of hydrobromic acid starting material to produce a sodium bromide yield equal to what our starting sodium hydroxide can produce theoretically. Therefore, hydrobromic acid is our limiting reagent. This deduction informs our final conclusion. We must disregard the calculation from Step 2b and instead go with that found in Step 2a:

mass = 95.6g NaBr

Hope this helps!

Cheers