Question 1

How much heat energy is gained when 5 kg of water at  20^o C is brought to its boiling point ( specific heat of water = 4.2   k g^{-1} c^{-1}  )

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Question 2

(a) When the air temperature is below   0^{\circ} C   , 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   -10^{\circ} C   and that the bottom surface it at   0^{\circ} C   , calculate the time it will take to form an ice sheet   25\,cm   thick.(d) If the lake in part (c) is uniformly   40\,m   deep , how  long would it take to freeze all the water in the lake ? Is this likely to occur ?

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Question 3

A thermistor is a solid - state device whose resistance varies greatly with temperature . Its temperature dependence is given approximately by $R = R_{0} e^{B / T}$ , where $R$ is in ohms $(Ω), T$ is in kelvin , and $R_{0}$ and $B$ are constants that can be determined by measuring $R$ at calibrations points such as the ice point and the steam point .
(a) If $R = 7360 (Ω)$ at the point and $153 (Ω)$ at the steam point , find $R_{0}$ and $B$
(b) What is the resistance of the thermistor at $t = 98 . 6^{\circ} F$ ?
(c) What is the rate of change of the resistance with temperature $(d R / d T)$ at the ice point and the steam point ?
(d) At which temperature is the thermistor most sensitive ?

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Question 4

The compound amongst following sublimes on heating is:

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Mercury (I) chloride a colorless solid is also known as calomel and reacts with chlorine to give mercuric chloride. Mercury (II) is the most common oxidation state and forms four mercuric halides. They form tetrahedral complexes with other ligands and mercury (II) chloride is an easy sublimating white solid.

Question 5

Which of the following solids are known to undergo sublimation?i.  \displaystyle { CO }_{ 2 } ii.  \displaystyle { I }_{ 2 } iii. Naphthalene

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Following solids are known to undergo sublimation :i.  CO_2 ii.  I_2 iii. NaphthaleneSublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. Sublimation is an endothermic phase transition that occurs at temperatures and pressures below a substance's triple point in its phase diagram. The reverse process of sublimation is desublimation or deposition, in which a substance passes directly from a gas to a solid phase. Sublimation has also been used as a generic term to describe phase changes between solid and gas that avoid the liquid state without specifying the direction of the transition.Hence the correct option is E.

Question 6

The sublimation temperature of a substance is $- 83^{o} C$ . It exist as cubic packed structure with unit cell edge length $5.0 \overset{˚}{A}$ and density $\frac{8}{3} g / c m^{3}$ , at $- 100^{o} C$ . What should be density of substance at $0^{o} C$ and $1 a t m$ ?
$(N_{A} = 6 \times 10^{23})$

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Question 7

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

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Sublimation is a type of phase transition, or a change in a state of matter, just like melting, freezing, and evaporation. Through sublimation, a substance changes from a solid to a gas without ever passing through a liquid phase. Dry ice, solid  CO_2  provides a common example of sublimation. "Dry ice" or solid  CO_2  sublimes.Snow and ice can sublime in the winter months without melting.Moth balls sublime.Frozen foods will sublime and you will find ice crystals inside of the box or bag. Related Links: Examples. Science Examples.

Question 8

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Atmosphere of moon has very less density because of absence of most of the gases since their rms speed is more than the escape velocity of moon. Hence, pressure on moon is very less and this increases the rate of evaporation significantly.Moon has 13.5 days of daytime and 13.5 days of night time. During daytime, temperatures can soar up to  123^o C . However, boiling is related to vaporization and not evaporation.

Question 9

The process  \displaystyle Solid\rightarrow Gas  is known as:

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Examples of Solid to Gas (Sublimation):  Dry Ice - Solid carbon dioxide is known as "dry ice" and sublimates at room temperature.

Question 10

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

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Important questions on Change Of State

How much heat energy is gained when 5 kg of water at $2 0^{o}$ C is brought to its boiling point ( specific heat of water = 4.2 $k g^{- 1} c^{- 1}$ )

1680 kJ

1700 kJ

1720 kJ

1740 kJ

The compound amongst following sublimes on heating is:

$H g C l_{2}$

$A g N O_{3}$

$Z n (N O_{3})_{2}$

$H g_{2} C l_{2}$

Which of the following solids are known to undergo sublimation?
i. $C O_{2}$
ii. $I_{2}$
iii. Naphthalene

i only

ii only

i and ii only

ii and iii only

i, ii and iii

The sublimation temperature of a substance is $- 83^{o} C$ . It exist as cubic packed structure with unit cell edge length $5.0 \overset{˚}{A}$ and density $\frac{8}{3} g / c m^{3}$ , at $- 100^{o} C$ . What should be density of substance at $0^{o} C$ and $1 a t m$ ?
$(N_{A} = 6 \times 10^{23})$

$50 g / c m^{3}$

$2.23 g / c m^{3}$

$2.23 g / l$

$1.86 g / l$

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

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

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

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

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

Assertion is correct but Reason is incorrect

Both Assertion and Reason are incorrect

The process $S o l i d \to G a s$ is known as:

sublimation

condensation

evaporation

deposition

melting

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

More important questions

Important questions on Change Of State

How much heat energy is gained when 5 kg of water at 20oC is brought to its boiling point ( specific heat of water = 4.2 kg−1c−1)

1680 kJ

1700 kJ

1720 kJ

1740 kJ

The compound amongst following sublimes on heating is:

HgCl2​

AgNO3​

Zn(NO3​)2​

Hg2​Cl2​

Which of the following solids are known to undergo sublimation? i. CO2​ ii. I2​ iii. Naphthalene

i only

ii only

i and ii only

ii and iii only

i, ii and iii

The sublimation temperature of a substance is −83oC. It exist as cubic packed structure with unit cell edge length 5.0A˚ and density 38​g/cm3, at −100oC. What should be density of substance at 0oC and 1atm? (NA​=6×1023)

50g/cm3

2.23g/cm3

2.23g/l

1.86g/l

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

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

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

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

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

Assertion is correct but Reason is incorrect

Both Assertion and Reason are incorrect

The process Solid→Gas is known as:

sublimation

condensation

evaporation

deposition

melting

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

More important questions

How much heat energy is gained when 5 kg of water at $2 0^{o}$ C is brought to its boiling point ( specific heat of water = 4.2 $k g^{- 1} c^{- 1}$ )

$H g C l_{2}$

$A g N O_{3}$

$Z n (N O_{3})_{2}$

$H g_{2} C l_{2}$

Which of the following solids are known to undergo sublimation?
i. $C O_{2}$
ii. $I_{2}$
iii. Naphthalene

The sublimation temperature of a substance is $- 83^{o} C$ . It exist as cubic packed structure with unit cell edge length $5.0 \overset{˚}{A}$ and density $\frac{8}{3} g / c m^{3}$ , at $- 100^{o} C$ . What should be density of substance at $0^{o} C$ and $1 a t m$ ?
$(N_{A} = 6 \times 10^{23})$

$50 g / c m^{3}$

$2.23 g / c m^{3}$

$2.23 g / l$

$1.86 g / l$

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

The process $S o l i d \to G a s$ is known as:

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