In water, 0 . 5 g of an impure sample of oxalate was dissolved, making the solution to 100 ml . 10 ml of this required 15 ml of N / 20 KMnO 4 solution on titration. Calculate the percentage of pure oxalate in the sample.

A solution of 15 ml of N / 20 KMnO 4 will have 15 / 20 milliequivalents of KMnO 4 No. of milliequivalents of Oxalate in 10 ml solution = 3 / 4 No. of milliequivalents of Oxalate in 100 ml solution = 30 / 4 Valence Factor of Oxalate = 2 Number of milliequivalents = number of millimoles × valence factor Number of millimoles of oxalate = 30 8 millimoles The molar mass of oxalate, C 2 O 2 2 - = 88 g mol - 1 Weight in grams of oxalate = 30 × 88 8 × 1000 g = 0 . 33 g % Pure oxalate = 0 . 33 0 . 5 × 100 = 66 %

Both Cr 2 O 7 2 - ( aq ) and MnO 4 - ( aq ) can be used to titrate Fe 2 + ( aq ) . If in a given titration, 24 . 50 cm 3 of 0 . 1 M Cr 2 O 7 2 - were used, then what volume of 0 . 1 M MnO 4 - solution will be consumed for the same titration in acidic medium?

Molarity of Cr 2 O 7 2 - = 0 . 1 M Molarity of MnO 4 - = 0 . 1 M Volume of Cr 2 O 7 2 - = 24 . 50 ml Volume of MnO 4 - needs to be calculated, Applying law of equivalence for titration between Fe 2 + and Cr 2 O 7 2 - Milliequivalents of Cr 2 O 7 2 - = Milliequivalents of Fe 2 + Milliequivalents = millimoles × valency factor Millimoles = Molarity × Volume in ml Millimoles of Cr 2 O 7 2 - = 0 . 1 × 24 . 5 Valency factor of Cr 2 O 7 2 - = 6 Milliequivalents of Cr 2 O 7 2 - = 0 . 1 × 24 . 5 × 6 = 14 . 7 Milliequivalents of Fe 2 + = 14 . 7 These much Fe 2 + will react with M n O 4 - Applying law of equivalence for titration between Fe 2 + and MnO 4 - Milliequivalents of MnO 4 - = Milliequivalents of Fe 2 + Milliequivalents of MnO 4 - = 14 . 7 Millimoles of MnO 4 - × Valency factor of MnO 4 - = 14 . 7 Valency Factor of MnO 4 - = 5 in acidic medium Millimoles of MnO 4 - = 14 . 7 5 = 2 . 94 Millimoles of MnO 4 - =Molarity of MnO 4 - × Volume of MnO 4 - in ml 2 . 94 = 0 . 1 × Volume of MnO 4 - Volume of MnO 4 - = 29 . 4 ml

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Important Questions on Some Basic Concepts, Mole Concept and Stoichiometry

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 1 - Some Basic Concepts, Mole Concept and Stoichiometry>DPP 1.5>Q 15

Which of the following concentration is correct for

13

mass percent of sulphuric acid (density:

1.09 g {mL}^{- 1}

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 1 - Some Basic Concepts, Mole Concept and Stoichiometry>DPP 1.5>Q 16

1 mole {BaF}_{2} + \underset{Resulting mixture}{1 mole H_{2} {SO}_{4} \underset{}{\to}}

will be neutralized by:

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 1 - Some Basic Concepts, Mole Concept and Stoichiometry>DPP 1.6>Q 1

In water,

0.5 g

of an impure sample of oxalate was dissolved, making the solution to

100 ml

10 ml

of this required

15 ml

N / 20 {KMnO}_{4}

solution on titration. Calculate the percentage of pure oxalate in the sample.

HARD

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 1 - Some Basic Concepts, Mole Concept and Stoichiometry>DPP 1.6>Q 2

Both

{Cr}_{2} O_{7}^{2 -} (aq)

and

{MnO}_{4}^{-} (aq)

can be used to titrate

{Fe}^{2 +} (aq)

. If in a given titration,

24.50 {cm}^{3}

0.1 M {Cr}_{2} O_{7}^{2 -}

were used, then what volume of

0.1 M {MnO}_{4}^{-}

solution will be consumed for the same titration in acidic medium?

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 1 - Some Basic Concepts, Mole Concept and Stoichiometry>DPP 1.6>Q 3

An impure sample of

{CaCO}_{3}

, that has moist clay as impurity, on heating, loses

14.5 %

of its weight of water.

5 g

of the sample shows a loss in weight by

1.507 g

. Calculate the percentage of

{CaCO}_{3}

in the sample.

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 1 - Some Basic Concepts, Mole Concept and Stoichiometry>DPP 1.6>Q 4

Calculate the weight of quick lime and soda ash required to soften one million litres of hard water containing dissolved salts as shown below:

$Ca ({HCO}_{3})_{2} = 48.6 ppm; {MgCl}_{2} = 19.0 ppm; {CaSO}_{4} = 68.0 ppm; {SiO}_{2} = 15.2 ppm$ .

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 1 - Some Basic Concepts, Mole Concept and Stoichiometry>DPP 1.6>Q 5

A mixture contains

{NaNO}_{3}, {AgNO}_{3}

and some impurities.

3.1 g

of the mixture was heated and the gases released were passed in pyrogallol. The weight of pyrogallol is increased by

0.208 g

. The residue left needs—for complete reaction—

25 mL

N / 10 HCl

. How much

{NaNO}_{3}

and

{AgNO}_{3}

is present in the mixture?

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Chapterwise/Topicwise Daily Practice Problems (DPP) Physical Chemistry Part 1 JEE Main & Advanced>Chapter 1 - Some Basic Concepts, Mole Concept and Stoichiometry>DPP 1.6>Q 6

A mixture contains $20 g$ of ${NaHCO}_{3}$ , $20 g$ of ${Na}_{2} {CO}_{3}$ and $20 g$ of $NaOH$ in a litre volume vessel. $55 mL$ of the mixture is titrated with $N HCl$ . What is the titer value, if phenolphthalein is added as the first indicator?

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Important Questions on Some Basic Concepts, Mole Concept and Stoichiometry

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