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51.

5 litre of a solution contains 25 mg of `CaCO_(3)`. What is its concentration in ppm? (mol.wt of `CaCO_(3)` is 100)A. 25B. 1C. 5D. 2500

Answer» Correct Answer - C
`"ppm"=("weight of solute"xx10^(6))/("weight of solution")`
`=(25xx10^(-3)xx10^(6))/(5000)=5`
Discussion
52.

The density (in g `mL^(-1))` of a `3.60M` sulphuric acid solution that is `29% H_(2)SO_(4)` (Molar mass `= 98 g mol^(-1))` by mass will beA. `1.64`B. `1.88`C. `1.22`D. `1.45`

Answer» Correct Answer - C
`"Molarity"=(10xx"density"xx"weight of solute")/("molecular weight of the solute")`
`"density"=(3.60xx98)/(10xx29)=1.216~~1.22`
Discussion
53.

Concentrated aqueous solution of sulphuric acid is `98 %` by mass and has density of `1.80 "g mL"^(-1)`. What is the volume of acid required to make one liter `0.1 M H_(2)SO_(4)` solution ?A. `11.10mL`B. `16.65mL`C. `22.20mL`D. `5.55mL`

Answer» Correct Answer - D
`"Normality"=("weight"%xx"density"xx10)/(eq.wt.)`
`=(98xx1.8xx10)/(49)=36N`
`becauseN_(1)V_(1)=N_(2)V_(2)`
`:.36xxV=0.2xx1000`
`V=5.55mL`
Discussion
54.

Which one of the following gases has the lowest value of Henry law constant ?A. `N_(2)`B. `He`C. `CO_(2)`D. `O_(2)`

Answer» Correct Answer - C
As the solubility incresases, `K_(H)` decreases. Among the given set of gases, `CO_(2)` is the most soluble in water. Hence, its `K_(H)` value is lowest.
Discussion
55.

25.3 g of sodium carbonate, `Na_(2)CO_(3)` is dissolved in enough water to make 250 mL of solution. If sodium carbonate dissociates completely, molar concentration of sodium ions, `Na^(+)` and carbonate ions, `CO_(3)^(2-)` are respectively (Molar mass of `NaCO_(3)=106g mol^(-1)`)A. `0.477Mand0.477MM`B. `0.955Mand1.910`C. `1.910Mand0.955M`D. `1.90Mand1.910M`

Answer» Correct Answer - C
`"Molarity"=(25.3xx1000)/(106xx250)=0.955M`
`Na_(2)CO_(3)to2Na^(+)+CO_(3)^(2-)`
`=2xx0.955+0.955M`
`=1.910M+0.955M`
`:.M_(Na^(+))=2xx0.955=1.910M`
`M_(CO_(3)^(2-))=0.955M`
Discussion
56.

`10cm^(3)` of 0.1N monobasic acid requires `15cm^(3)` of sodium hydroxide solution whose normality isA. `1.5N`B. `0.15N`C. `0.066N`D. `0.66N`

Answer» Correct Answer - C
`{:(N_(1)V_(1),=,N_(2)V_(2)),(("For monobasic acid"),,("For NaOH")):}`
`10xx0.1N=15xxN_(2)`
`N_(2)=(1N)/(15)=0.066N`
Discussion
57.

The vapour pressures of ethanol and methanol are `44.5` and `88.7 mm Hg`, respectively. An ideal solution is formed at the same temperature by mixing `60 g` of ethanol with `40 g` of `methanol`. Calculate the total vapour pressure of the solution and mole fraction of methanol in the vapour.

Answer» Correct Answer - `0.657`
Discussion
58.

Equal masses of methane and oxygen are mixed in an empty container at `25^(@)C`. The fraction of the total pressure exerted by oxygen is:A. `(2)/(3)`B. `(1)/(3)xx(273)/(298)`C. `(1)/(3)`D. `(1)/(2)`

Answer» Correct Answer - C
Suppose the equal mass of methane and oxygen `=w=1g`
`"Mole fraction of oxygen"=(w//32)/(w//32+w//16)=(1)/(3)`
Let the total pressure =p
Pressure exerted by oxygen (partial pressure)
`=x_(O_(2))xxP_("total")=Pxx(1)/(3)`
Discussion
59.

Dissolution of 1.5 g of a non-volatile solute `(mol.wt.=60)` in 250 g of a solvent reduces its freezing point by `0.01^(@)C`. Find the molal depression constant of the solvent.A. `0.01`B. `0.001`C. `0.0001`D. `0.1`

Answer» Correct Answer - D
Depression in freezing point, `DeltaT_(f)=K_(f)xxm`
`DeltaT_(f)=K_(f)xxm`
`"where,m=molality"=("wt.of solute"xx 1000)/("mol.wt.of solute"xxwt.of" solvent")` "
`=(1.5xx1000)/(60xx250)=0.1`
`DeltaT_(f)=K_(f)xx0.1`
`0.01=K_(f)xx0.1`
`:.K_(f)=(0.01)/(0.1)=0.1^(@)C kg" mol"^(-1)`
Discussion
60.

Solute is non-volatile and solvent molecule is volatile. Which of the following has maximum contribution in vapour phase ?A. SoluteB. solventC. Solute and solvent bothD. None of these

Answer» Correct Answer - B
When the solute is non-volatile, only the solvent molecule are present in the vapour phase and contribute to vapour pressure.
Discussion
61.

If M is molecular of solvent, `K_(b)` is molal elevation constant, `T_(b)` is its boiling point, `P^(@)` is its vapour pressure at temperature T and `P_(s)` is vapour pressure of its solution having a non-volatile solute at T K, thenA. `(p^(@)-p_(s))/(p^(@))=(DeltaT_(b))/(K_(b))xxM`B. `(p^(@)-p_(s))/(p^(@))=(K_(b))/(T_(b)xxM)`C. `(p^(@)-p_(s))/(p^(@))=(K_(b))/(T_(b))xx(M)/(1000)`D. `(p^(@)-p_(s))/(p^(@))=(DeltaT_(b))/(K_(b))xx(M)/(1000)`

Answer» Correct Answer - D
`(p^(@)-p_(s))/(p^(@))=(n)/(N)=("Molality"xxM)/(1000)`
`"and " "molality"=(DeltaT_(b))/(K_(b))" " (becauseDeltaT_(b)=K_(b)xxm)`
Discussion
62.

The molal elevation constant of water =`0.52 K m^(-1)`. The boiling point of `1.0 molal` aqueous `KCl` solution (assuming complete dissociation of `KCl`) should beA. `98.96^(@)C`B. `100.52^(@)C`C. `101.04^(@)C`D. `107.01^(@)C`

Answer» Correct Answer - C
`DeltaT_(b)=iK_(b)m=2xx1xx0.52=1.04`
`:.T_(b)=T_(b)^(@)+DeltaT_(b)=100+1.04`
`101.4^(@)C`
Discussion
63.

At `25^(@)C`, the highest osmotic pressure is exhibited by 0.1 M solution of :A. ureaB. glucoseC. KCID. `CaCl_(2)`

Answer» Correct Answer - D
(d) More the number of ions is solution more will be the osmotic pressure of solution.
`CaCl_(2)toCa^(2+)+2Cl^(-)(3" ions")`
`:.CaCl_(2)` produces maximum number of ions.
`:.` It will have highest osmotic pressure.
Discussion
64.

A solution containing 4g of polyvinyl chloride polymer in 1 L of dioxane was found to have an osmotic pressure of `4.1xx10^(-4)` atm at `27^(@)C`. The approximate molecular weight of the polymer isA. 1500B. 10000C. `2.4xx10^(5)`D. `2xx10^(12)`

Answer» Correct Answer - C
`becausepi=CRT=(n)/(V)RT`
`pixxV=nRT=(w)/(m)RT`
`m=(wRT)/(pixxV)=(4xx0.0821xx(27+273))/(4xx10^(-4)xx1)`
`2.4xx10^(5)`
Discussion