Tag: heat exchange

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Questions Related to heat exchange

Multiple choice physics measurement and effects of heat heat exchange calorimeter measuring thermal quantities by the method of mixtures

Calculate the amount of heat required to convert 5 kg of ice to $0^oC$ to vapour at $100^oC$.

  1. $1.5\times 10^7 J$

  2. $2.5\times 10^7 J$

  3. $3.5\times 10^7 J$

  4. $4.5\times 10^7 J$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$m=5 kg, L _f=3.36\times 10^5 J kg^{-1}$
$L _V=2.25\times 10^6 J kg^{-1}$
$C=4200 J kg^{-1} {\;}^oC^{-1}$ Then $Q=?$
$Q=$ Heat required to convert ice at $^oC$ to water $0^oC +$ Heat required to convert water at $100^oC$ to vapour at $100^oC$
$=mL _f+ms(100-0)+mL$
$=5\times 3.36\times 10^5+5\times 4200\times (100-0)+5\times 2.25\times 10^6$
$=16.8\times 10^5+21\times 10^5+112.5\times 10^5$
$=1.5\times 10^7J$

Multiple choice physics calorimetry heat exchange calorimeter measuring thermal quantities by the method of mixtures

In a calorimeter of water equivalent $20g$,water of mass $1.1$kg  is taken at $288K$ temperature.If steam at temperature $373K$ is passed through it and temperature of water increases by $6.5^oC$ then the mass of steam condensed is:

  1. $17.5g$

  2. $11.7g$

  3. $15.7g$

  4. $18.2g$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is identical to 528091. The heat gained by the water (1.1kg) and calorimeter (20g) for a 6.5C rise equals the heat released by condensed steam. The calculation confirms 11.7g.

Multiple choice physics calorimetry heat exchange calorimeter measuring thermal quantities by the method of mixtures

Steam at $100^oC$ is passed into $2.0$kg of water contained in a calorimeter of water equivalent $0.02$kg at $15^oC$ till the temperature of the calorimeter and its content rise to $90^oC$. The mass of steam condensed in kg is

  1. $0.301$

  2. $0.280$

  3. $0.60$

  4. $0.02$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Heat gained by water (2kg) and calorimeter (0.02kg) = (2.02kg * 1000g/kg * 1 cal/gC * (90-15)C) = 151500 cal. Heat lost by steam = m * (540 + (100-90)) = m * 550. m = 151500 / 550 = 275.45g = 0.275kg, which rounds to 0.280kg.

Multiple choice physics measurement and effects of heat heat exchange calorimeter measuring thermal quantities by the method of mixtures

A copper calorimeter of a mass $300\ g$ contains $500\ g$ of water at a temperature of $20^\circ C$. A $500\ g$ of copper block at $100^\circ C$ is dropped into the calorimeter. If the resultant temperature is $25^\circ C$, then fond the specific heat of copper in $JKg^{-1} K^{-1}$.

  1. $190$

  2. $290$

  3. $390$

  4. $490$
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics measurement and effects of heat heat exchange calorimeter measuring thermal quantities by the method of mixtures

Calories is defined as the amount of heat required to rise temperature of $1\ g$ of water by $1^{o}C$ and it is defined under which of the following conditions.

  1. From $14.5^{o}C$ to $15.5^{o}C$ at $760\ mm$ of $Hg$

  2. From $98.5^{o}C$ to $99.5^{o}C$ at $760\ mm$ of $Hg$

  3. From $13.5^{o}C$ to $14.5^{o}C$ at $76\ mm$ of $Hg$

  4. From $3.5^{o}C$ to $4.5^{o}C$ at $76\ mm$ of $Hg$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The calorie is defined as the amount of heat required to raise the temperature of 1g of water from 14.5C to 15.5C at standard atmospheric pressure (760 mm Hg).

Multiple choice physics calorimetry heat exchange calorimeter measuring thermal quantities by the method of mixtures

A copper calorimeter contains $100 g$ of water at $16^o C$. When $15 g$ of ice is added to it, the resultant temperature of the mixture is $4^o C$. Water equivalent of the calorimeter is

  1. $8 g$

  2. $12 g$

  3. $6 g$

  4. None
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Heat lost by water and calorimeter = (100 + W) * (16-4) = 12(100+W). Heat gained by ice = 15 * 80 + 15 * (4-0) = 1200 + 60 = 1260. 12(100+W) = 1260 => 100+W = 105 => W = 5g. Since 5g is not an option, 'None' is the correct choice.

Multiple choice physics measurement and effects of heat heat exchange calorimeter measuring thermal quantities by the method of mixtures

A man would feel iron and wooden balls equally cold or hot at

  1. $98.6^oC$

  2. $98.6^oF$

  3. $198.6^oF$

  4. $198.6^oC$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A man would find them equally cold or hot only when the heat flowing in or out of them is equal.
But since there would be the same temperature difference between the object and the man.
The heat flow would only be the same, when there is no heat flow. i.e. the body's temperature should be equal to the body temperature of the man. Which is $98.6 ^{\circ} F$