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Citric acid, the predominant acid in lemon juice, is a triprotic acid - HSC - SSCE Chemistry - Question 14 - 2009 - Paper 1
Question 14
Citric acid, the predominant acid in lemon juice, is a triprotic acid. A student titrated 25.0 mL samples of lemon juice with 0.550 mol L$^{-1}$ NaOH. The mean titra... show full transcript
Worked Solution & Example Answer:Citric acid, the predominant acid in lemon juice, is a triprotic acid - HSC - SSCE Chemistry - Question 14 - 2009 - Paper 1
Step 1
Calculate the moles of NaOH used
Step 2
Calculate the moles of citric acid
Answer
Citric acid is a triprotic acid, which means it can react with three moles of NaOH. Therefore, the moles of citric acid can be calculated as:
ext{Moles Citric Acid} = rac{ ext{Moles NaOH}}{3} = rac{0.016225}{3} = 0.00540833 ext{ moles}
Step 3
Calculate the concentration of citric acid
Answer
To find the concentration of citric acid in g L, we use:
ext{Concentration (g L$^{-1}$)} = rac{ ext{Moles Citric Acid} imes ext{Molar Mass}}{ ext{Volume of lemon juice (L)}}
Substituting the values:
ext{Concentration} = rac{0.00540833 imes 192.12}{0.025} = 41.6 ext{ g L$^{-1}$}