Chemistry Test

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Chemistry Test - 1

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Weekly Quiz Competition

Question 1
1 / -0

How many moles of magnesium phosphate Mg₃(PO₄)₂ will contain 0.25 moles of oxygen atoms?

A
2.15 x 0.02

B
3.125 x 10^-2

C
1.25 x 10^-2

D
2. 5 x 10^-2

Solution

In $\mathrm{Mg}_{3}\left(\mathrm{PO}_{2}\right)_{2}$ one molecule of it contains 8 atoms of oxygen
$\because B$ moles of oxygen atoms are present in 1 mole $\mathrm{Mg}_{3}\left(\mathrm{PO}_{4}\right)_{2}$
$\therefore 0.25$ mole of oxygen atoms are present in
$$
\frac{0.25}{8}=3.125 \times 10^{-2} \text {moles of } M g_{3}\left(P O_{4}\right)_{2}
$$
Hence, option, B is correct answer
Question 2
1 / -0

How many moles of Na₂S₂O₃ can be produced from 32 g of sulphur?

A
1.0

B
0.50

C
79

D
158

Solution

Number of moles of sulphur = 32/32 = 1 mole
One mole of Na₂S₂O₃ will be obtained from 2 moles of sulphur.
Mole of Na₂S₂O₃ obtained from 1 mole of sulphur = ½ = .50 mole
Hence, option, B is correct answer
Question 3
1 / -0

What is the approximate number of molecules in 4.25 g of NH₃?

A
1 x 10²³

B
1.5 x 10²³

C
2 x 10²³

D
6 x 10²³

Solution

Number of moles of ammonia = 4.25/17 = 0.25 mol
Number of molecules in 0.25 mol of ammonia = 0.25 x 6.022 x 10²³
= 1.5 x 10²³
Hence, option, B is correct answer
Question 4
1 / -0

What volume of 0.1 M ethanol is required for the preparation of 5.6 g of C₂H₄ using concentrated H₂SO₄?

A
2000 mL

B
400 mL

C
200 mL

D
1 L

Solution

$C H_{3}-C H_{2}-O H \stackrel{H_{2} S O_{4}}{\longrightarrow} C H_{2}=C H_{2}+H_{2} O$
46 g 28 g
It is clear from the above equation that number of moles of ethene formed = Number of moles of ethanol used
Number of moles of ethene formed = 5.6/28 = 0.2
M = n/V
V = n/M = 0.2/0.1 = 2 L
Hence, option, A is correct answer
Question 5
1 / -0

What is the number of atoms in 100 amu of He? (Atomic weight of He is 4 u)

A
25

B
100

C
50

D
125

Solution

Mass of 1 atom of helium = 4 amu
Number of Atoms = $\frac{N u m b e r o f a t o m i c m a s s u n i t}{A t o m i c M a s s' H e'}$
So, in 100 amu, the number of helium atoms = 100/4 = 25 helium atoms
Hence, option, A is correct answer
Question 6
1 / -0

Which gas has the highest partial pressure in atmosphere?

A
CO₂

B
H₂O

C
0₂

D
N₂

Solution

Nitrogen is present in largest amount in the atmosphere. So it has the highest partial pressure in the atmosphere.
Hence, option, D is correct answer
Question 7
1 / -0

Ratio between r.m.s. velocity of hydrogen at 50 K and that of oxygen at 800 K is

A
4

B
2

C
1

D
1/4

Solution

$\frac{v_{1}}{v_{2}} = \sqrt{\frac{3 R T_{1}}{M_{1}} \times \frac{M_{2}}{3 R T_{2}}}$
$\sqrt{\frac{T_{1} M_{2}}{T_{2} M_{1}}} = \sqrt{\frac{50 \times 32}{800 \times 2}} = 1$
Hence, option, C is correct answer
Question 8
1 / -0

Which of the following does not crystallise in the rock-salt structure?

A
NaCl

B
KCl

C
MgO

D
CsCl

Solution

CsCL has body-centred cubical packing.
Hence, option, d is correct answer
Question 9
1 / -0

The partial pressure of hydrogen in a flask containing 2 g of H₂ and 32 g of SO₂ is

A
1/16 of total pressure

B
1/2 of total pressure

C
2/3 of total pressure

D
1/8 of total pressure

Solution

The partial pressure of A in a mixture of A and other gases is the total pressure multiplied by the mole fraction of A.
In the present case,
Mole fraction of hydrogen =1/(1+(1/2)) = 2/3
The partial pressure of Hydrogen = 2/3 of total pressure
Hence, option, C is correct answer
Question 10
1 / -0

The number of orbitals associated with quantum numbers n = 5, m_s = +1/2 is:

A
5

B
15

C
125

D
25

Solution

We have:
n - 5, m_s = +1/2
Thus, values of l are from 0 to (n-1)
l = 0 to 4
Thus, values of l are 5s, 5p, 5d, 5f and 5g
Now, the total number of orbitals = n² = 5² = 25
Hence, option, D is correct answer

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Chemistry Test - 1

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Question 1

2.15 x 0.02

3.125 x 10-2

1.25 x 10-2

2. 5 x 10-2

Solution

Question 2

1.0

0.50

79

158

Solution

Question 3

1 x 1023

1.5 x 1023

2 x 1023

6 x 1023

Solution

Question 4

2000 mL

400 mL

200 mL

1 L

Solution

Question 5

25

100

50

125

Solution

Question 6

CO2

H2O

02

N2

Solution

Question 7

4

2

1

1/4

Solution

Question 8

NaCl

KCl

MgO

CsCl

Solution

Question 9

1/16 of total pressure

1/2 of total pressure

2/3 of total pressure

1/8 of total pressure

Solution

Question 10

5

15

125

25

Solution

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3.125 x 10^-2

1.25 x 10^-2

2. 5 x 10^-2

1 x 10²³

1.5 x 10²³

2 x 10²³

6 x 10²³

CO₂

H₂O

0₂

N₂