1. Commerchaol lye is an alkaline mixture that contains mainly sodium hydroxide,
ID: 924415 • Letter: 1
Question
1. Commerchaol lye is an alkaline mixture that contains mainly sodium hydroxide, but major impurities include sodium chloride, sodium carbonate, sodium chlorate, sodium sulfate, potassium and heavy metals such as iron and nickel. A 0.8500 g sample of commercial lye is dissolved in water and titrated with 35.00 mL of 0.5377 M HCl.
What is the percent purity of lye sample? (i.e., what is the mass percent of NaOH in the lye?)
2. A 0.3811 g sample of KOH will just neutralize what volume of 0.2000 M H2SO4 ?
What volume of 0.2000 M H2SO4 will just neutralize the KOH sample?
Explanation / Answer
moles of HCl in 35ml of 0.5377= 0.5377*35/1000=0.01882
The reaction between NaOH and HCl is given by NaOH+ HCl -----> NaCl+ H2O
moles of NaOH consumed by HCl =0.01882
Mass of NaOH= 0.01882* Molecular weight= 0.01882*40= 0.753 gm
Mass percent of sanple= 0.753*100/0.85= 88.58 %
2. 2KOH+ H2SO4----> K2SO4+ 2H2O is the reaction
mass of KOH= 0.3811 Molecular weight of KOH= 56
Moles of KOH= 0.3811/56= 0.006805
2 moles of KOH requiews 1 mole of H2SO4
0.006805 moles require 0.006805*1/2 =0.003403 moles
0,2M =0.2 moles/ Liter
0.2 moles are there in 1 Liters
0.003403 moles correspond to 0.003403*1/0.2= 0.017013 L =17.013 ml
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