# First Year Chemistry Solutions 3. How much salt will be required to prepare following solutions (atomic mass: \mathrm{K}=39 ; \mathrm{Na}=23 ; \mathrm{S}=32 ; 0=16 and \mathrm{H}=\mathrm{l} )b. 600 \mathrm{~cm}^{3} of \math

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##### 3. How much salt will be required to prepare following solutions (atomic mass: \mathrm{K}=39 ; \mathrm{Na}=23 ; \mathrm{S}=32 ; 0=16 and \mathrm{H}=\mathrm{l} )b. 600 \mathrm{~cm}^{3} of \mathrm{NaN} 0_{3} solution of 0.25 \mathrm{M}

Worked Example 2: The pH of a solution is 9.63. Compute its hydrogen ion concentration.

(b) Give the oxidation number of:(vi) \mathrm{O} in \mathrm{OF}_{2}

Example 2: The oxidation of \mathrm{FeSO}_{4} by \mathrm{KMnO}_{4} in acidic solution

10. Tyndall effect is due to:(a) blockage of beam of light(b) non-scattering of beam of light(c) scattering of beam of light(d) passing through beam of light

6. A hiker walks due east at 4 \mathrm{~km} per hour and a second hiker starting at the same point walks 55^{\circ} north-east at the rate of 5 \mathrm{~km} per hour. How far apart will they be after 3 hours?

\mathrm{Q} 21.4 .675 \mathrm{~g} of a compound with empirical formula \mathrm{C}_{3} \mathrm{H}_{3} \mathrm{O} were dissolved in 212.5 \mathrm{~g} of pure benzene. The freezing point of solution was found 1.02^{\circ} \mathrm{C} less than that of pure benzene. The molal freezing point constant of benzene is 5.1^{\circ} \mathrm{C} . Calculate (i) the relative molar mass and (ii) the molecular formula of the compound.

What is molarity and give its formula to prepare molar solution?

Find radii r_{1} r_{2} r_{3} of the escribed-circles of a \triangle A B C in the following:9. Prove that r_{1}=4 R \sin \frac{\alpha}{2} \cos \frac{\beta}{2} \cos \frac{\gamma}{2}=(s-c) \cot \frac{\beta}{2}

3. What is electrolysis? Explain by giving the example of \mathrm{CuCl}_{2} . Give all necessary electrode reactions.

2. Which one of the following is a liquid in solidsolution?(a) sugar in water(b) butter(c) opal(d) fog

4. How will you test whether given solution is a colloidal solution or not?

5. Two hikers start from the same point; one walks 9 \mathrm{~km} heading east the other one 10 \mathrm{~km} heading 55^{\circ} north east. How far apart are they at the end of their walks?

9. Tyndall effect is shown by:(a) sugar solution(b) paints(c) jelly(d) chalk solution

Q 23. 3 g of a non-volatile non-electrolyte solute X are dissolved in 50 \mathrm{~g} of ether (molar mass = 74) at 293 \mathrm{~K} . The vapour pressure of ether falls from 442 torr to 426 torr under these conditions. Calculate the molar mass of solute X .(Ans: 122.6 \mathrm{~g} \mathrm{~mol}^{-1} )

Worked Example 1: What is the pH of 0.004 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCl} (fully dissociated) at 25^{\circ} \mathrm{C} .

7. Balance the following equations by ion electron method.(ii) \mathrm{MnO}_{4}^{-1}+\mathrm{SO}_{3}^{2-}+\mathrm{H}_{+}^{-} \longrightarrow \mathrm{Mn}^{+2}+\mathrm{SO}_{4}^{2-}

Examples (2):Calculate the molarity of a solution containing 20.7 \mathrm{~g} of \mathrm{K}_{2} \mathrm{CO}_{3} dissolved in 500 \mathrm{~cm}^{3} of the given solution.

(c) Calculate the concentration of a solution in terms of molality which is obtained by mixing 250 \mathrm{~g} of 20 \% solution of \mathrm{NaCl} with 200 \mathrm{~g} of 40 \% solution of \mathrm{NaCl} .

1. A solution contains 50 \mathrm{~g} of sugar dissolved in 450 \mathrm{~g} of water. What is concentration of this solution?

Q13. What is Raoults law. Give its three statements. How this law can help us to understand the ideality of a solution.

11. If 10 \mathrm{~cm}^{3} of alcohol is dissolved in 100 \mathrm{~g} of water it is called:(a) \% \mathrm{w} / \mathrm{w} (b) \% \mathrm{w} / \mathrm{v} (c) \% \mathrm{v} / \mathrm{w} (d) \% \mathrm{v} / \mathrm{V}

3. Why the suspension does not form a homogeneous mixture?

What is saturated solution and how it is prepared?

11. What are strong and weak acids and bases? Give appropriate examples.

5. Classify the following into true solution and colloidal solution:Blood starch solution glucose solution toothpaste copper sulphate solution silver nitrate solution.

Q6. Explain the following with reasonsvi) The total volume of the solution by mixing 100 \mathrm{~cm}^{3} of water with 100 \mathrm{~cm}^{3} of alcohol may not be equal to 200 \mathrm{~cm}^{3} . Justify it.

Q6. Explain the following with reasonsviii) Non-ideal solutions do not obey the Raoults law.

Example.2 Given that a=15 \cdot 2 \mathrm{~cm} b=20 \cdot 9 \mathrm{~cm} and c=34 \cdot 7 \mathrm{~cm} solve the triangle.