Question

Sodium hydroxide is sold commercially as solid lye. A 0.308 g sample of lye required 22.5 mL of 0.250 M HCl to neutralize it. Calculate the percentage by mass of NaOH in lye.

Answer 1

To calculate the percentage by mass of NaOH in lye, you need to find the moles of NaOH and the mass of NaOH in the sample. This can be done using the balanced chemical equation, molar mass of NaOH, and the given information.

Step-by-step explanation:

The balanced chemical equation for the reaction between NaOH and HCl is:

NaOH + HCl → NaCl + H2O

To calculate the percentage by mass of NaOH in lye, we need to find the number of moles of NaOH and the mass of NaOH in the sample:

1. Calculate the moles of HCl used: moles of HCl = volume (L) × concentration (M)
   
2. From the balanced equation, we know that 1 mole of NaOH reacts with 1 mole of HCl. So, the moles of NaOH in the sample is equal to the moles of HCl used.
   
3. Calculate the mass of NaOH: mass of NaOH = moles of NaOH × molar mass of NaOH
   
4. Calculate the percentage by mass: percentage by mass = (mass of NaOH / mass of lye) × 100
   

Using the given information, the percentage by mass of NaOH in lye is X%