Class 12th Chemistry 2017 Set1 Outside Delhi Board Paper Solution
(b) Define the following terms:
(i) Molality (m)
(ii) Abnormal molar mass
OR
(a) 30g of Urea (M = 60 g mol-1) is dissolved in 846 g of water. calculate the vapour pressure of water for this solution if vapour pressure of pure water at 298 K is 23.8 mm Hg.
(b) Write two difference between ideal solution and non-ideal solutions.
(b)
(i) Molality is defined as the number of moles of solute per kilogram of solvent. The SI unit for molality is mol/kg.
(ii) Abnormal molar masses and colligative properties. For the solute which undergo association or dissociation, observed value of colligative property is different from the calculated value of colligative property.
OR
(a) Vapour pressure of water, p1 = 23.8 mm of Hg
Weight of water = 846 g
Weight of urea = 30 g
Molecular weight of water (H2O) = 1 × 2 + 16 = 18 g mol−1
Molecular weight of urea (NH2CONH2) = 2N + 4H + C + O
= 2 × 14 + 4 × 1 + 12 + 16
= 60 g mol−1
Number of moles of water n1 = 846 / 18 = 47
Number of mole of urea n2 = 30 / 60 = 0.5
Now, we have to calculate vapour pressure of water in the solution. We take vapour pressure as p1.
Use the formula of Raoult’s law
(P10 - P1) / P10 = n2 / (n1-n2)
Plug the values we get
(23.8 - p1) / 23.8 = 0.5 / (47+0.5)
(23.8 - p1) / 23.8 = 0.5106
after cross multiply
23.8 – p1 = 23.8 × 0.5106
Solve it we get p1 = 11.6 mm Hg
So, Vapour pressure of water in the given solution = 11.6 mm of Hg
(b)
| Ideal Solution | Non-ideal Solution |
| Obey Raoult's law at every range of concentration. | Do not obey Raoult's law. |
 Neither heat is evolved nor absorbed during dissolution. |
 Endothermic dissolution; heat is absorbed. |
Popular Questions of Class 12th chemistry
- Q:-
How the following conversions can be carried out?
(i) Propene to propan-1-ol
(ii) Ethanol to but-1-yne
(iii) 1-Bromopropane to 2-bromopropane
(iv) Toluene to benzyl alcohol
(v) Benzene to 4-bromonitrobenzene
(vi) Benzyl alcohol to 2-phenylethanoic acid
(vii) Ethanol to propanenitrile
(viii) Aniline to chlorobenzene
(ix) 2-Chlorobutane to 3, 4-dimethylhexane
(x) 2-Methyl-1-propene to 2-chloro-2-methylpropane
(xi) Ethyl chloride to propanoic acid
(xii) But-1-ene to n-butyliodide
(xiii) 2-Chloropropane to 1-propanol
(xiv) Isopropyl alcohol to iodoform
(xv) Chlorobenzene to p-nitrophenol
(xvi) 2-Bromopropane to 1-bromopropane
(xvii) Chloroethane to butane
(xviii) Benzene to diphenyl
(xix) tert-Butyl bromide to isobutyl bromide
(xx) Aniline to phenylisocyanide
- Q:-
Give simple chemical tests to distinguish between the following pairs of compounds.
(i) Propanal and Propanone
(ii) Acetophenone and Benzophenone
(iii) Phenol and Benzoic acid
(iv) Benzoic acid and Ethyl benzoate
(v) Pentan-2-one and Pentan-3-one
(vi) Benzaldehyde and Acetophenone
(vii) Ethanal and Propanal
- Q:-
A 5% solution (by mass) of cane sugar in water has freezing point of 271 K. Calculate the freezing point of 5% glucose in water if freezing point of pure water is 273.15 K.
- Q:-
A solution of glucose in water is labelled as 10% w/w, what would be the molality and mole fraction of each component in the solution? If the density of solution is 1.2 g mL-1, then what shall be the molarity of the solution?
- Q:-
Henry's law constant for CO2 in water is 1.67 x 108Pa at 298 K. Calculate the quantity of CO2in 500 mL of soda water when packed under 2.5 atm CO2 pressure at 298 K.
- Q:-
Calculate the mass of a non-volatile solute (molar mass 40 g mol-1) which should be dissolved in 114 g octane to reduce its vapour pressure to 80%.
- Q:-
The vapour pressure of pure liquids A and B are 450 and 700 mm Hg respectively, at 350 K. Find out the composition of the liquid mixture if total vapour pressure is 600 mm Hg. Also find the composition of the vapour phase.
- Q:-
Calculate the mole fraction of benzene in solution containing 30% by mass in carbon tetrachloride.
- Q:-
How many mL of 0.1 M HCl are required to react completely with 1 g mixture of Na2CO3 and NaHCO3 containing equimolar amounts of both?
- Q:-
If NaCl is doped with 10-3mol % of SrCl2, what is the concentration of cation vacancies?
Recently Viewed Questions of Class 12th chemistry
- Q:-
What is a semiconductor? Describe the two main types of semiconductors and contrast their conduction mechanism.
- Q:-
Why is Ka2 << Ka1 for H2SO4 in water?
- Q:-
Give two reactions that show the acidic nature of phenol. Compare acidity of phenol with that of ethanol.
- Q:-
Explain why inspite of nearly the same electronegativity, oxygen forms hydrogen bonding while chlorine does not.
- Q:-
Vapour pressure of water at 293 Kis 17.535 mm Hg. Calculate the vapour pressure of water at 293 Kwhen 25 g of glucose is dissolved in 450 g of water.
- Q:-
What are enzymes?
- Q:-
What is the covalence of nitrogen in N2O5?
- Q:-
Draw figure to show the splitting of d orbitals in an octahedral crystal field.
- Q:-
Name the following halides according to IUPAC system and classify them as alkyl, allyl, benzyl (primary, secondary, tertiary), vinyl or aryl halides:
(i) (CH3)2CHCH(Cl)CH3
(ii) CH3CH2CH(CH3)CH(C2H5)Cl
(iii) CH3CH2C(CH3)2CH2I
(iv) (CH3)3CCH2CH(Br)C6H5
(v) CH3CH(CH3)CH(Br)CH3
(vi) CH3C(C2H5)2CH2Br
(vii) CH3C(Cl)(C2H5)CH2CH3
(viii) CH3CH=C(Cl)CH2CH(CH3)2
(ix) CH3CH=CHC(Br)(CH3)2
(x) p-ClC6H4CH2CH(CH3)2
(xi) m-ClCH2C6H4CH2C(CH3)3
(xii) o-Br-C6H4CH(CH3)CH2CH3
- Q:-
Write the equations for the preparation of 1-iodobutane from
(i) 1-butanol
(ii) 1-chlorobutane
(iii) but-1-ene.