Date: 14/09/12
Chemistry
Class-11
First Term Exam
Time : 3 hours
Total marks: 70
1.
Which of the following orbitals are not possible and why? 7s, 4d ,3f and 1p
1
2.
Give the values of the quantum numbers for the electron with the highest energy in sodium atom?
1
3.
What is the main difference between the radiations emitted by a bulb or a heater and that
associated with a particle?
1
4.
What is the effect of temperature on molarity of a solution?
1
5.
Which is more concentrated, 1 m or 1 M NaOH aqueous solution? (Na=23, O=16, H=1)
1
6.
A gas that follows Boyle’s law, Charle’s law and Avogadro’s law is called an ideal gas. Under what
conditions a real gas would behave ideally?
1
7.
Two different gases A and B are filled in separate containers of equal capacity under the same
conditions of temperature and pressure. On increasing the pressure slightly the gas A liquefies but
gas B does not liquefy even on applying high pressure. Explain.
1
8.
Which will form a more stable ionic bond:
(i)
Group 1 element & Group 17 element or
(ii)
Group 2 element & Group 17 element?
Explain briefly.
1
9.
What is the wavelength of light emitted when the electron in a hydrogen atom undergoes
transition from an energy level with n=4 to an energy level with n = 2 using Rydberg’s formula?
2
10.
(a) Write the configuration of Fe+3 and Co+2. (Fe=26; Co=28)
(b) Which of the above species is more paramagnetic?
2
11.
Draw the shape of orbitals having quantum no’s n=3, l=2
2
12.
a) Predict the position for element A with atomic number 47
b) Predict any two properties of element A
2
13.
a) What would be the IUPAC name and symbol for the element with atomic number 116
b) How would you justify the presence of 18 elements in the 5th period of the periodic table.
2
14.
In the reaction 2A + 4B → 3C + 4D, if 5 moles of A reacts with 6 moles of B,
(i)
Which is the limiting reagent?
(ii)
Calculate the amount of C formed.
2
15.
A sugar syrup of weight 214.2 g contains 34.2 g sugar. Calculate mole fraction of sugar in syrup.
Molar mass of sugar is 342 g/mol.
2
16.
The magnitude of surface tension of liquid depends on the attractive forces between the
molecules. Arrange the following in increasing order of surface tension: water, alcohol
(CH3CH2OH), and ethane (CH3CH3). Also justify your answer.
OR
2
1
(a) Give difference between normal and standard boiling points
(b) Critical temperature of CO2 & CH4 are 31.1°C & -81°C respectively. Which of these has
strong intermolecular forces and why?
17.
18.
(c) Liquid X has stronger intermolecular forces than liquid Y. Which, out of the two has high
viscosity?
(d) Ammonia reacts with chlorine gas to form ammonium chloride. Can we apply Dalton’s law
of partial pressures to this mixture? Explain.
Give two examples each of:
(a) Molecules with central atom having expanded octet.
(b) Molecules with odd electrons.
2
2
19.
(a) Arrange the following ions in order of decreasing ionic radii, giving reasons what are these 3
ions called? Li+2,He+1,Be+3
(b) Why Vanderwaals radii of an element is always larger than the covalent radii?
20
(a) Na+ is smaller in size than Na whereas Cl-1 is larger than Cl. Explain.
(b) A, B, C are three elements with atomic numbers Z-1, Z, Z+1 respectively. B is an inert gas.
Answer the following questions:
(i)
Predict the group of A and C.
(ii)
Which of the three has positive electron gain enthalpy and why?
3
21.
Neon gas emits radiations strongly at 616 nm. Calculate
(a) the frequency of emissions
(b) energy of quantum
(c) Number of quanta present if it produces 2 Joules of energy.
(h=6.6x10-34 j-sec; c=3x10-8 m/sec)
3
22.
The work function for Caesium atom is 1.9 eV. Calculate
(a) the threshold wavelength
(b) If Cesium is irradiated with light of wavelength 500nm , calculate kinetic energy of the
ejected photoelectron.(h=6.6x10-34 j-sec; c=3x10-8 m/sec; eV=1.6x10-19 J)
3
23.
(a) Calculate the % NH2 & %CO in urea CO(NH2)2. N=14, C=12, H=1, O=16.
(b) Give an example in which ratio of molecular formula and empirical formula is 6:1.
(c) Explain giving examples law of constant proportions.
3
24.
The reaction: 2Br - (aq) + Cl2(aq) → 2Cl-(aq) + Br2(aq) is used for the commercial preparation of Br2
from its salts. Suppose we have 50 mL of 0.06 M solution of NaBr, what volume of 0.05 M Cl2 is
needed to react completely with Br-?
3
25.
Two gases A and B having molecular masses 60 and 45 respectively are enclosed in a vessel. The
mass of A is 0.5 g and that of B is 0.2 g. The total pressure of the mixture is 0.921 bar. Calculate the
partial pressures of the two gases.
3
26.
An open vessel at 27°C is heated until three-fifth of the air has been expelled. Assuming that the
volume of air is constant, find the temperature to which vessel has been heated.
OR
(a) What do Vanderwaal’s parameter ‘a’ & ‘b’ stand for?
(b) What is the value of compressibility factor’ Z’ for an ideal gas?
(c) How do the following vary with temperature: (i) viscosity (ii) vapour pressure?
3
2
27.
Draw the Lewis dot structures of NH4+, CO & PCl3 and calculate the formal charge on the
underlined atoms.
3
28.
i) Among the elements B, Al, C and S
a) Which element has highest ionisation enthalpy?
b) Which has the most negative electron gain enthalpy?
c) Which has the longest atomic radii?
d) Which has the most metallic character?
2
ii) Define electron gain enthalpy. How does it vary across a period?
iii) 20Ca and30 Zn have same electrons in the valence shell. Their valence electrons are also same,
yet they belong to different groups. Justify
2
1
OR
29.
30.
(i) The First (Δ H1) and Second ( Δ H2)Ionisation Enthalpy (kj/mol) of three elements A, B, C are
given below
A
B
C
Δ H1
403
549
1142
Δ H2
2640
1060
2080
Giving reasons identify the element which is likely to be
a) non-metal
b)an alkali metal
c)an alkaline earth metal giving reasons
3
(ii) Explain why:a) Boron has a lower ionisation enthalpy than Berylium
b) Electron gain enthalpy of fluorine is less negative than that of chlorine.
2
a) Explain the following
(i)
Quantisation of electronic energy
(ii)
Hund’s rule of maximum multiplicity
b) Explain any two main defects of Bohr’s model.
c) What is the significance of ψ and ψ2
OR
a) Explain photoelectric effect on the basis of Planck’s quantum theory.
b) By what names are the following principles known?
(i)
electron with the same spin quantum cannot be present in the same
atomic orbital.
(ii)
Electrons occupy a lower energy orbital before occupying a higher energy orbital.
2
(a) A sample of nitrogen gas occupies a volume of 1.0 dm3 at a pressure of 0.5 bar and 40°C.
Calculate the pressure of the gas if compressed to 0.225 dm3 at -6°C.
(b) A sample of helium gas has volume 500 mL at 373 K. Calculate the temperature at which
the volume becomes 260 mL. Assume that pressure remains constant.
OR
(a) A 34 dm3 cylinder contains 212 g of oxygen gas at 21°C. What mass of oxygen must be
released to reduce the pressure in the cylinder to 1.24 bar?
(b) A gas at a pressure of 5.0 bar is heated from 0°C to 546°C and simultaneously compressed
to one-third of its original volume. What will be the final pressure?
3
3
2
1
3
2
2
3
2
CH. CHAPTER
NO.
5
STRUCTURE OF ATOM
3
PERIODIC PROPERTIES
1
BASIC CONCEPT
2
4
STATES OF MATTER
CHEMICAL BONDING
1 MARK
2 MARK
3 MARK
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
4
5 MARKS
TOTAL
MARKS
12
5
17
6