JEE Main · 2023 · 13 Apr 2023 · Shift 1 · Practical and Analytical Chemistry

20 mL of calcium hydroxide was consumed when it was reacted with 10 mL of unknown solution of

H_{2} SO_{4}

. Also 20 mL standard solution of 0.5 M HCl containing 2 drops of phenolphthalein was titrated with calcium hydroxide the mixture showed pink colour when burette displayed the value of 35.5 mL whereas the burette showed 25.5 mL initially. The concentration of

H_{2} SO_{4}

____

M (Nearest integer)

Answer: 1

Solution

First, determine the concentration of

Ca (OH) X_{2}

from the HCl titration. The reaction is

Ca (OH) X_{2} + 2 HCl CaCl X_{2} + 2 H X_{2} O

. Volume of

Ca (OH) X_{2}

used = 35.5 - 25.5 = 10 mL. Millimoles of HCl = 20 × 0.5 = 10. From stoichiometry, millimoles of

Ca (OH) X_{2}

= 10/2 = 5. Therefore, molarity of

Ca (OH) X_{2}

= 5/10 = 0.5 M.

For the reaction with

H X_{2} SO X_{4}

Ca (OH) X_{2} + H X_{2} SO X_{4} CaSO X_{4} + 2 H X_{2} O

. Millimoles of

Ca (OH) X_{2}

= 20 × 0.5 = 10. From 1:1 stoichiometry, millimoles of

H X_{2} SO X_{4}

= 10. Therefore, molarity of

H X_{2} SO X_{4}

= 10/10 = 1 M.

JEE Main · 2023 · 13 Apr 2023 · Shift 1 · Integer answer

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JEE Main · 2023 · 13 Apr 2023 · Shift 1 · Practical and Analytical Chemistry

Solution

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