Heat Problems



Heat Problems (answers)

Mr. pressly is the best

Calculate the following. Show your work and write out the formula you use. Specific heat water, steam and ice on yellow packet.

1. How much heat is required to raise the temperature of 300.0 grams of aluminum from 22oC to 55oC? The specific heat of aluminum is 0.21 cal/g oC.

Q= mC(T 300(0.21)(33) = 2079cal

2. How much heat in joules is required to raise the temperature of 25.0 grams of liquid water from 9 oC to 29 oC?

Q= mC(T 25(4.18)20 = 2090J

3. How much heat is absorbed when 56.8 grams H2O at 100 oC and 1 atm is converted to steam at 100oC? Give answer in kilojoules.

Q=mHv 56.8g(2260) = 128368J = 128.368kJ

4. How much heat is required to raise the temperature of 132.0 grams of chloroform from 58oC to 89oC? The specific heat of chloroform is 0.96 J/g oC.

Q= mC(T 132.0 g(0.96)(31) = 3928.32

5. How much heat in joules is required to raise the temperature of 34.0 grams of liquid water from 10 oC to 67 oC?

Q= mC(T 34.0g (4.18) (57) = 8100.84

6. How many kilojoules are required to melt a 18.0 g popsicle at 0 oC. Assume the popsicle has the same heat of fusion as water.

Q=mHf 18.0g(334J/g) = 6012J =6.012kJ

7. How much heat is required to convert 34.0 grams of water at 45 oC completely to steam at 100 oC? (2 steps)

1st step Q= mC(T 2nd step Q=mHv add two together

=34.0(4.18)(55) =34.0g(2260) 7816.6 + 76840 = 84656.6

= 7816.6J =76840J

8. How much heat is required to convert 65.0 grams of ice at -5 oC completely to water at 0 oC? (2 steps)

1st step Q= mC(T 2nd step Q=mHf add two together = 22376.25 J

C= 2.05 for ice

65 (2.05)(5) + 65(334)

9. How much heat is required to convert 1.0 grams of ice at 0 oC completely to water at 0 oC? Q=mHf = 334J

10. How much heat is required to raise the temperature of 1.89 X 102 grams of iron from 3K to 45K? The specific heat of iron is 0.46 J/g oC.

Q= mC(T 189g (.46)(42K) = 3651.48

11. How many grams of ice at 0 oC could be melted by the addition of 1.2 joules of heat?

Q= mHf 1.2J = m (334) solve for m = .0036gram or 3.6 X10-3

12. How much heat is required to change 2.4 moles of liquid ammonia to gas at its normal boiling point. The heat of vaporization of ammonia is 23.4 kJ/mol.

Q= mHv 2.4mole X 23.4 kJ/mol = 56.16 kJ

13. How much heat is required to change 4.23 moles of solid oxygen to liquid at its normal melting point. The heat of fusion of O2 is 0.44 kJ/mol.

4.23 mole X .44 kJ/mol Q= mHf = 1.86 kJ

14. How much heat is required to change 35.4 grams of liquid methanol to gas at its normal boiling point. The heat of vaporization of methanol is 35.3 kJ/mol.

Q= mHf 35.4/32g (mass of methanol) = 1.10 moles X 35.3 kJ/mol = 39.05 kJ

15. How much heat in joules is required to convert 2.5 moles of solid aluminum from 23 oC to 45oC?

Yellow packet specific heat of aluminum

Q= mC(T 2.5mol X 27g/mol = 67.5 g (.897j/g oC)(22 oC) = 1332.045 J

16. How much heat in joules is required to convert 1.00 mole of water from 45oC to 18oC? What is happening to the water?

Q= mC(T get negative heat, cooling down 18grams(4.18J/g)(27) = 2031 J

17. How much heat is required to convert 8.7 moles of ice at -4 oC completely to steam at 100 oC? Be careful (more than one step)

8.7 moles X 18g/mol = 156.6 grams H2O 4 steps

Q= mC(T Q= mHf Q= mC(T Q= mHv

156.6(2.05)(4) 156.6(334) 156.6(4.18)(100) 156.6(2260) =472,963J

18. How much heat is required to convert 56.9 grams of ice at -2 oC completely to water at 100 oC? Be careful (more than one step)

Q= mC(T Q= mHf Q= mC(T

56.9(2.05)(2)=233.29 + 56.9(334)=19004.6 + 56.9(4.18)(100)=23784.2 = 43022.09J

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