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$3. How much salt will be required to prepare following solutions (atomic mass: \mathrm{K}=39 ; \mathrm{Na}=23 ; \mathrm{S}=32 ; 0=16 and \mathrm{H}=\mathrm{l} )b. 600 \mathrm{~cm}^{3} of \mathrm{NaN} 0_{3} solution of 0.25 \mathrm{M}$  $Worked Example 2: The pH of a solution is 9.63. Compute its hydrogen ion concentration.$  $(b) Give the oxidation number of:(vi) \mathrm{O} in \mathrm{OF}_{2}$  $Example 2: The oxidation of \mathrm{FeSO}_{4} by \mathrm{KMnO}_{4} in acidic solution$  $10. Tyndall effect is due to:(a) blockage of beam of light(b) non-scattering of beam of light(c) scattering of beam of light(d) passing through beam of light$  $6. A hiker walks due east at 4 \mathrm{~km} per hour and a second hiker starting at the same point walks 55^{\circ} north-east at the rate of 5 \mathrm{~km} per hour. How far apart will they be after 3 hours?$  $\mathrm{Q} 21.4 .675 \mathrm{~g} of a compound with empirical formula \mathrm{C}_{3} \mathrm{H}_{3} \mathrm{O} were dissolved in 212.5 \mathrm{~g} of pure benzene. The freezing point of solution was found 1.02^{\circ} \mathrm{C} less than that of pure benzene. The molal freezing point constant of benzene is 5.1^{\circ} \mathrm{C} . Calculate (i) the relative molar mass and (ii) the molecular formula of the compound.$  