Tag: law of constant proportion - i

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Multiple choice chemistry atoms, molecules and chemical reactions law of constant proportion - i law of constant proportion law of definite proportions

Statement: Every nine parts of water by weight contain eight parts by weight of oxygen. 


State whether the given statement is true or false.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Water (H2O) has a molar mass of 18 g/mol (2*1 + 16). The mass ratio of oxygen to water is 16/18, which simplifies to 8/9. Thus, 9 parts of water contain 8 parts of oxygen.

Multiple choice evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

The process of obtaining salt from sea water involves:

  1. evaporation

  2. condensation

  3. sublimation

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The process of obtaining salt from sea water involves the process evaporation is used an a large scale to obtain common salt from sea water. Sea water is trapped in shallow lakes and allowed to stand there. The heat of sun gradually evaporates water in the shallow lakes and common salt is left behind as a solid. Sea water has many salts dissolved in it.
Multiple choice evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

Changing of liquid into vapours without heating is called:

  1. freezing

  2. steaming

  3. evaporation

  4. none of above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Changing of liquid into vapours is called evaporation and it causes cooling.
And in freezing the liquid changes into solid and causes cooling.
And in steaming the liquid boils and changes in vapour but causes heating
Multiple choice evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

Rainfall is related to which process?

  1. Evaporation

  2. Condensation

  3. Sublimation

  4. Heating
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation

The water vapor rises in the atmosphere due to heating of water by sunlight and there it cools down and forms tiny water droplets through something called condensation. When they all combine together, they grow bigger and are too heavy to stay up there in the air. This is when they will fall to the ground as rain, or maybe snow or hail by gravity.

Sublimation is not involved in rainfall process

Multiple choice evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

The thermal resistance of heat transfer is low in:

  1. Drop wise condensation

  2. Filmwise condensation

  3. Bulk wise condensation

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The thermal resistance of heat transfer is low in drop wise condensation.


 Thermal resistance is a heat property and a measurement of a temperature difference by which an object or material resists a heat flow.

Multiple choice evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

When you get in your car in the morning and are breathing warmer air, the warm air comes into contact with the cooler windshield and forms a foggy window. It is an example of :

  1. evaporation

  2. sublimation

  3. condensation

  4. both A and C
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Condensation is the process by which water vapor in the air is changed into liquid water.Cloud formation is caused by condensation of water vapor in the atmosphere condensing into a liquid state. Thus Option C is correct.

Multiple choice evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

The process of changing water vapour into water is called:

  1. boiling

  2. evaporation

  3. melting

  4. condensation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The process of changing water vapour into water is called condensation.

Condensation is simply the process of change of the vapour from gaseous state to liquid when comes in contact of cool surface.
And this process can't be boiling as in boiling we have to provide heat and it is the change of liquid state into vapour form.
And the process is not evaporation as it also changes water into vapour.
Melting is not the required process as it is the change of state from solid to liquid.

Multiple choice evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

Evaporation causes:

  1. cooling

  2. heating effect

  3. an increase in weight

  4. an increase in density
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Evaporation causes cooling.

Because in evaporation the water changes form liquid to vapour state so the vapour of water causes the surface to becomes cool.
Evaporation causes cooling because during evaporation the particle of the liqued absord energy from the surroundings to regain the energy lost during evaporation. the absorbtion of heat from the surrounding makes the surrounding  cool.

Multiple choice evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

Which of the following is an example of evaporation?

  1. Drying of hair

  2. Preparation of common salt from sea water

  3. Dew in the morning

  4. Cooling of hot tea
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation
Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase.
Drying of leads to water loss in hair or water evapouration leads to water evapouration.
Producing of salt also leads of water evaporation from salted water.
Cooling of hot tea leads to water codensation not evaporation.