1.
Name the anion and cation which constitute the molecule of magnesium
oxide [1]
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2. A cube of side 5cm is
immersed in water and then in saturated salt solution. In which case will it
experience a greater buoyant force. If each side of the cube is reduced to
4cm and then immersed in water compare the force experienced by the cube, as
compared to the first case. Give reasons for each case. 2
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4. The percentage of
three elements calcium, carbon and oxygen in a sample of calcium carbonate is
given as : [3]
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Calcium =40% ; Carbon
=12.0% ; Oxygen = 48%
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If the law of constant
proportion is true, what weights of these elements will be present in 1.5 g
of another sample of calcium. Carbonate ? (Atomic mass of Ca = 40 u, C
= 12 u, O = 16 u)
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5. The description of atomic particles of two
elements X and Y is given below[3]
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| ||||||||||||
(i) What is the atomic
number of Y?
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(ii) What is the mass
number of X?
| ||||||||||||
(iii) What is the
relation between X and Y?
| ||||||||||||
(iv) Which
element/elements do they represent?
| ||||||||||||
(v) Write the electronic
configuration of X?
| ||||||||||||
(vi) Write the
cation/anion formed by the element
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6. Which of the
following are isotopes and which are isobars?
| ||||||||||||
Argon, Protium, Calcium,
Deuterium. Explain why the isotopes have similar chemical properties but they
differ in physical properties? [3]
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7.What do you mean by
buoyancy? Why does an object float or sink when placed on the surface of
water?[3]
| ||||||||||||
8. When is the work done
by a force said to be negative? Give one situation in which one of the forces
acting on the object is doing positive work and the other is doing negative
work. [3]
| ||||||||||||
9. Define one Joule of
work. Calculate the work done in lifting a box weighting 150 kg through a
vertical height of 7 meters (take g=10 ms2) [3]
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10. A construction
worker’s helmet slips and falls when he is 78.4 m above the ground. He hears
the sound of the helmet hitting the ground 4.23 seconds after it slipped.
Find the speed of sound on air. [3]
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11. Answer these questions[5]
| ||||||||||||
(i) Define mole
| ||||||||||||
(ii) How is it related
to Avogadro constant, relative mass and molecular mass?
| ||||||||||||
(iii) What is the number
of molecules in 0.25 moles of oxygen ? Avogadro’s no. = 6 .22 x1023.
| ||||||||||||
OR
| ||||||||||||
(i) Define atomicity
| ||||||||||||
(ii) Give an example
each of a polyatomic element and a polyatomic ion.
| ||||||||||||
(iii) How many atoms are
present in CaCl2 molecule and ion? SO4-2
| ||||||||||||
(iv) Write down the
formulae of
| ||||||||||||
(a) sodium carbonate
| ||||||||||||
(b) Ammonium chloride
| ||||||||||||
(c) Zinc oxide
| ||||||||||||
(d) Aluminium hydroxide
| ||||||||||||
12. (i) An object thrown
at a certain angle to the ground moves in a curved path and falls back to the
ground. The initial and the final points of the path of the object lie on the
same horizontal line. What is the total work done against the force of gravity
and by the force of gravity on the object? Explain with proper mathematical
expressions.
| ||||||||||||
(ii) Certain force
acting on 20kg mass changes its velocity from 5ms-1 to 2ms-1 calculates the
work done by the force. [5]
| ||||||||||||
OR,
| ||||||||||||
(i) Define kinetic
energy. Derive an expression for the kinetic energy of an object.
| ||||||||||||
(ii) The power of a
motor pump is 5kW. How much water per minute the pump can raise to height of
20m? Take g=10ms-2
|
Solution:
1.
|
Magnesium oxide – MgO
Anion – O-2
Cation – Mg+2
|
½
½
|
|||||
2
|
We know buyant force =
V.P g
V = Volume of body
P = density of liquid
g = acceleration
Since density of
saturated salt solutions is more than water the cube will experience greater
upthrust.
In second case as volume
of cube is less then first so in 2nd case it will experience less upthrust
|
½
½
½
½
|
|||||
3
|
Initial K.E = 25J
Since K.E
=
½ mv2 D as velocity doubles K.S
becomes 4 times
K.E = 4x25=100J
|
1
1
|
|||||
4
|
Mass of calcium in 1.5 g of sample = 40 x [1.5/100] =
9.6 g
Mass of carbon in 1.5 g of sample = 12x [1.5/100] =
0.18 g
Mass of oxygen in 1.5 g of sample = 48x[1.5/100] =
0.72 g
|
1
1
1
|
|||||
5
|
(i) Atomic number of y –
8
(ii) Mass number of x –
16
(iii) x and y are
isotopes
(iv) x and y represent –
oxygen
(v) 168O
- 2, 6
(vi) It will form an
anion – O-2
|
1
1
1
|
|||||
6
|
Isotopes – Protium,
Diuterium
Isobars – Argon and
calcium
Since isotopes have
identical electronic configuration containing same number of valence
electrons they have similar chemical properties.
Since the masses are
slightly different the physical properties (density, melting pt, boiling pt,
etc) are different
|
1
1
|
|||||
7
|
When a body is immersed
in a fluid, it experiences an upward force. This upward force is the force of
buoyancy.
Forces acting an the
body inside water are buoyant force weight of body and if the buoyant force
is greater than the gravitational force it floats, otherwise it sinks.
|
1
2
|
|||||
8
|
Negative work – When the
force is acting opposite to the direction of the displacement, the work done
by the force is taken as negative.
When we lift an object
two forces act on the object.
Muscular force – Doing
positive work in the direction of the displacement.
Gravitational force –
doing negative work opposite to the direction of the displacement.
|
1
1
1
|
|||||
9
|
One Joule is the amount
of work done on an object when a force of 1N displaces it by 1 m along the
line of action of force
m = 150kg ; G = 10m/s2 ;
h = 7m
P.E = mgh
P.E = 150 x 10 x7 =
10500J
|
1
2
|
|||||
10
|
We know, h = ut + 1/2 gt2
u =
0, h =
78.4, g =
9.8 m/s2
using these
t2 = 16 Þ
t = 4 s
time taken by the helmet reach the ground = 4 s
Þ
time taken by sound to reach the height =
4.23 – 4 =
0.23s
ÞSpeed
of sound = 78.4 /0.23 = 340.87 m/s
|
1
1
1
|
|||||
11
|
(i) Mole – one mole of
any species (atoms, molecules, ions or particles) is that quantity in number
having a mass equal to its atomic or molecular mass in grams
(ii) 1 mole = 6.022 x
1023 in number – Relative mass in g.
(iii) 1 mole of oxygen
contain 6.022 x 1023 molecules
0.25 mole of oxygen
contain 6.022 x1023 x 0.25
= 1.505 x 1023 molecules
|
1
2
2
|
|||||
OR
|
(i) Atomicity – Number
of atoms constituting a molecule
(ii) Polyatomic element
– sulphur
Polyatomic ion – NH4-, OH-, SO4-2
(any one)
(iii) Cacl2 – atomicity – 3
SO4-2 – atomicity - 5
(iv) (a) Na2CO3 Sodium carbonate
(b) NH4Cl Ammonium chloride
(c) ZnO zinc oxide
(d) Al(OH)3 Aluminium hydroxide
|
1
½+½
½+½
½+½+
½+½
|
|||||
12.
|
(i) Work done =
mgh
Difference in height of initial and final position is
zero.
Work done =
mg ( h2 -
h1)
= mg(o) = O
(ii) Work done = change in K.E
Work done = 1/2 m
(v12 – v22) = ½ x 20(52 - 22) = 210 J
|
1
½
1
1
½
|
|||||
OR
|
|||||||
(i) Energy posesed by a
body by virtue of motion.
F = ma
W =
F.S =
mas
But u2 -
v2 =
2as Þ as =
½ (v2-u2)
w = energy Þ
S = v2/2a
m. a x x v2 x 2a = 1/2mv2
|
½
½
½
½
|
||||||
(ii) Energy = power x
time =
5kw x 1 min = 3 x 105 J
mgh = E /gh = (3
x 105)/ 10x 20 = 1.5 x 103
kg
volume of water
= mass/ density = (1.5 x 103
)/103 = 1.5 m3
|
½
½
1
|
||||||
13
|
(i)
|
||||||
(ii)
|
Eardrum moves inwards
when compression reaches it and moves outwards when rarefaction reaches it
thus the ear drum vibrates.
(ii) Audible rang 20Hz
to 20,000 Hz
OR
|
||||||
(i)
|
Ceiling and walls are
made curved so that sound after reflection reaches the target audience.
(ii) Reflection
The sound goes to the
obstacle and reaches back the ear of the listeners on reflection after 0.1s.
If speed of sound in air is 344 m/s
then the minimum
distance of obstacle from the source of sound must be 17.2 cm
(iii) Repeated
reflection of sound that results in persistence of sound- Reverberation.
sound is blurred,
distorted, confusing
sound absorbent material
on roof, walls, seats
|
||||||
CBSE SUMMATIVE ASSESSMENT-II SAMPLE PAPER 2014
Class Xth [Links]
|
CBSE SUMMATIVE
ASSESSMENT-II SAMPLE PAPER 2014 Class IXth [Links]
|
