States of Matter Test

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States of Matter Test - 29

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Weekly Quiz Competition

Question 1
1 / -0

The correct expression of partial pressure in terms of mole fraction is :

A
$$p_{1} = x_{1}P_{total}, p_{2} = x_{2}P_{total}$$

B
$$p = x_{1}x_{2}P_{total}$$

C
$$P_{total} = p_{1}x_{1}, P_{total} = p_{2}x_{2}$$

D
$$p_{1} + p_{2} = x_{1} + x_{2}$$

Solution

If $$x_{1}$$ and $$x_{2}$$ are mole fractions of two gases.
Their partial pressures are $$p_{1} = x_{1} P_{total}, p_{2} = x_{2} P_{total}$$.
Question 2
1 / -0

The pressure of a $$1 : 4$$ mixture of dihydrogen and dioxygen enclosed in a vessel is one atmosphere. What would be the partial pressure of dioxygen?

A
$$0.8\times 10^{4} atm$$

B
$$0.008\ N\ m^{-2}$$

C
$$8\times 10^{4} N\ m^{-2}$$

D
$$0.25\ atm$$
Solution
Correct Option: Option C

Hint: $$P_{partial} \propto n_{gas}$$

Explanation

Step 1: Preparing data
- We know that, $$P_{partial} = \chi_{gas} \times P_{total}$$ where, …$$(1)$$
  $$P_{partial}=$$ Partial pressure of gas
  $$\chi_{gas}=$$ mole fraction of gas
  $$P_{total}=$$ Total pressure of mixture of gases
- Also, $$\chi_{n_{1}} = \dfrac{n_{1}}{n_{1} + n_{2} + n_{3} + n_{n}}$$ …$$(2)$$
  where, $$\chi_{n_{1}} =$$ Mole fraction of gas $$1$$
  $$n_{1} , n_{2} , n_{3}$$ and $$n_{n}= $$ Moles of all gases in mixture
- Given, $$P_{total} = 1$$ atm.
  And, $$\dfrac{n_{H_2}}{n_{O_2}} = \dfrac{1}{4}$$
Step 2: Solving using equations
- $$n_{H_2} = x$$ and $$n_{O_2} = 4x$$
- Therefore, $$Moles_{(total)} = 5x$$
- Thus, $$\chi_{H_2} = \dfrac{1}{5}$$ and $$\chi_{O_2} = \dfrac{4}{5}$$
- Putting above values in equation $$(1)$$, we get:
  $$P_{partial} ({O_2}) = \dfrac{4}{5} \times 1$$ atm
- Now, $$1$$ $$atm \approx 10^5$$ $$N/m^2$$
- Therefore, $$P_{partial} ({O_2}) = \dfrac{4}{5} \times 1 \times 10^5$$ $$N/m^2$$
Hence, $$ P_{O_{2}} = 8 \times 10^4$$ is the partial pressure of dioxygen.
Question 3
1 / -0

Dipole-dipole forces act between the molecules possessing permanent dipole. Ends of dipoles possess 'partial charges'. The partial charge is:

A
more than unit electronic charge

B
equal to unit electronic charge

C
less than unit electronic charge

D
double the unit electronic charge

Solution

Partial charges are always less than the unit electronic charge $$(1.6\times 10^{-19}C)$$.
Question 4
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According to kinetic theory of gases, the collisions between molecules of a gas:

A
occur in a zig-zag path

B
occur in a straight line

C
change velocity and energy

D
result in settling down of molecules

Solution

Particles of a gas collide in a straight line in all possible directions.
Question 5
1 / -0

The kinetic theory of matter helped a great deal in understanding the behaviour of gases. Which of the following statements did not belong to it?

A
When the gas is heated by raising its temperature the molecules move faster

B
The molecules in a gas are always moving

C
Gases are made up of small particles called molecules

D
When molecules collide, they lose energy

Solution

When molecules collide, they lose energy.
The kinetic theory states that, no energy is gained or lost when molecules collide.
Hence, statement D does not belongs to the kinetic theory of gas.
Question 6
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Which scientist discovered that the same amount of space was occupied by equal numbers of molecules of gases, irrespective of whether it was hydrogen or chlorine or fluorine?

A
Gay-Lussac

B
Avogadro

C
Marconi

D
Wohler

Solution

Avogadro first discovered it.
It states that $$1$$ $$mole$$ of any element or compound have $$6.022\times 10^{23}$$ atoms or molecules present at any constant temperature and pressure.
Question 7
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Which of the following assumptions is incorrect according to kinetic theory of gases?

A
Particles of a gas move in all possible directions in straight lines

B
All the particles, at any particular time, have same speed and same kinetic energy

C
There is no force of attraction between the particles of a gas at ordinary temperature and pressure

D
The actual volume of the gas is negligible in comparison to the empty space between them

Solution

Gases are made up of a large number of particles. They travel in a straight line until there take places a collision between them and an object (eg: wall of the container). They don't have any force of attraction with walls of the container. The average kinetic energy depends on the temperature of the gas.
Question 8
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Which of the following is correct?

A
Van der waals radius of chlorine is bigger than nitrogen.

B
Covalent radius of nitrogen is bigger than chlorine.

C
Van der waals radius of chlorine is smaller than nitrogen.

D
All are correct.

Solution

Answer:- (A) van der waals radius of chlorine is bigger than nitrogen
Van der waals radius of chlorine = 175 pm
Van der waals radius of nitrogen = 155 pm
Hence A is correct answer.
Question 9
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Equal masses of helium and oxygen are mixed in a container at $$25^{\circ}C$$. The fraction of the total pressure exerted by oxygen in the mixture of gases is :

A
$$1/3$$

B
$$2/3$$

C
$$1/9$$

D
$$4/9$$

Solution

Mole fraction of $$O_{2} = \dfrac {\dfrac {w}{32}}{\dfrac {w}{32} + \dfrac {w}{4}} = \dfrac {w}{32}\times \dfrac {32}{9w} = \dfrac {1}{9}$$
Partial pressure of oxygen $$= P \times x_{O_{2}}$$
$$= P_{total}\times \dfrac {1}{9}$$ or $$\dfrac {1}{9}P_{total}$$.
Question 10
1 / -0

As the temperature increases, average kinetic energy of molecules increases. What would be the effect of increase of temperature on pressure provided the volume is constant?

A
Increases

B
Decreases

C
Remains same

D
Becomes half

Solution

Gay Lussac's law states that at constant volume, pressure of a fixed amount of a gas varies directly with the temperature.

$$\therefore P\propto T$$ (at constant volume)

Thus, if temperature is increased at constant volume pressure increases.

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States of Matter Test - 29

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States of Matter Test - 29

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Question 1

$$p_{1} = x_{1}P_{total}, p_{2} = x_{2}P_{total}$$

$$p = x_{1}x_{2}P_{total}$$

$$P_{total} = p_{1}x_{1}, P_{total} = p_{2}x_{2}$$

$$p_{1} + p_{2} = x_{1} + x_{2}$$

Solution

Question 2

$$0.8\times 10^{4} atm$$

$$0.008\ N\ m^{-2}$$

$$8\times 10^{4} N\ m^{-2}$$

$$0.25\ atm$$

Solution

Question 3

more than unit electronic charge

equal to unit electronic charge

less than unit electronic charge

double the unit electronic charge

Solution

Question 4

occur in a zig-zag path

occur in a straight line

change velocity and energy

result in settling down of molecules

Solution

Question 5

When the gas is heated by raising its temperature the molecules move faster

The molecules in a gas are always moving

Gases are made up of small particles called molecules

When molecules collide, they lose energy

Solution

Question 6

Gay-Lussac

Avogadro

Marconi

Wohler

Solution

Question 7

Particles of a gas move in all possible directions in straight lines

All the particles, at any particular time, have same speed and same kinetic energy

There is no force of attraction between the particles of a gas at ordinary temperature and pressure

The actual volume of the gas is negligible in comparison to the empty space between them

Solution

Question 8

Van der waals radius of chlorine is bigger than nitrogen.

Covalent radius of nitrogen is bigger than chlorine.

Van der waals radius of chlorine is smaller than nitrogen.

All are correct.

Solution

Question 9

$$1/3$$

$$2/3$$

$$1/9$$

$$4/9$$

Solution

Question 10

Increases

Decreases

Remains same

Becomes half

Solution

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