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Important questions on Change Of State

HARD

How much heat energy is gained when 5 kg of water at C is brought to its boiling point ( specific heat of water = 4.2 )

A

1680 kJ

B

1700 kJ

C

1720 kJ

D

1740 kJ

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HARD

(a) When the air temperature is below , the water at the surface of a lake freezes to from an ice sheet. Why doesn't freezing occur throughout the entire volume of the lake?
(b) Show that the thickness of the ice sheet formed on the surface of a lake is proportional of the surface root of the time if the heat of fusion of the water freezing on the underside of the ice sheet is conducted through the sheet.
(c) Assuming that the upper surface of the ice sheet is at and that the bottom surface it at , calculate the time it will take to form an ice sheet thick.
(d) If the lake in part (c) is uniformly deep , how  long would it take to freeze all the water in the lake ? Is this likely to occur ?

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HARD

A thermistor is a solid - state device whose resistance varies greatly with temperature . Its temperature dependence is given approximately by , where is in ohms is in kelvin , and and are constants that can be determined by measuring at calibrations points such as the ice point and the steam point . 
(a) If at the point and at the steam point , find and  
(b) What is the resistance of the thermistor at
(c) What is the rate of change of the resistance with temperature at the ice point and the steam point ? 
(d) At which temperature is the thermistor most sensitive ?

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HARD

The compound amongst following sublimes on heating is:

A

B

C

D

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HARD

Which of the following solids are known to undergo sublimation?
i. 

ii. 
iii. Naphthalene

A

i only

B

ii only

C

i and ii only

D

ii and iii only

E

i, ii and iii

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HARD

The sublimation temperature of a substance is . It exist as cubic packed structure with unit cell edge length and density , at . What should be density of substance at and ?

A

B

C

D

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HARD

Give a brief description of the principles of the following process taking an example.
Sublimation.

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HARD
Assertion

Water, kept in an open vessel, will quickly evaporate on the surface of the moon.

Reason

The temperature at the surface of the moon is much higher than boiling point of water.

A

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

B

Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

C

Assertion is correct but Reason is incorrect

D

Both Assertion and Reason are incorrect

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HARD

The process is known as: 

A

sublimation

B

condensation

C

evaporation

D

deposition

E

melting

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HARD

How will you obtain the following?
Mercury from corrosive sublimate.

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