Answer:
- 25080 J
- 146.9 g
- 92.58 °C
- 0.808 J/g°C
- 117.09 g
- a. 1708.8 kJ b.1246.56 kJ
- 368.55 kJ
- 6.81 kJ
- 5.50 grams of methane produces more heat than 5.5 grams of propane.
Explanation:
- The specific heat capacity of water=4.18 J/gK
The enthalpy change is calculated using the formula: ΔH=MC∅ where ΔH is the change in enthalpy, M the mass of the substance, C the specific heat capacity of the substance and ∅ the temperature change.
Thus, ΔH= 750g × 4.18 J/gK × (19-11)K
=25080 J
2. Enthalpy change= mass of substance × specific heat capacity of the substance× Change in temperature.
ΔH= MC∅
M= ΔH/(C∅)
Substituting for the values in the question.
M=8750 J/(0.9025/g°C×66.0 °C)
=146.9 grams
3. Enthalpy change =mass × specific heat capacity × Temperature
ΔH= MC∅
∅ = ΔH/(MC)
=6500 J/(250 g × 4.18 J/g°C)
=6.22° C
Final temperature =98.8 °C - 6.22°C
=92.58 °C
4. Specific heat capacity =mass × specific heat capacity × Temperature change.
ΔH=MC∅
C= ΔH/(M∅)
Substituting with the values in the question.
C = 4786 J/(89.0 g×(89.5° C-23°C))
=0.808 J/g°C
5. Heat lost lost copper is equal to the heat gained by water.
ΔH(copper)= ΔH(water)
MC∅(copper)=MC∅(water)
M×0.385 J/g°C× (75.6°C- (19.1 °C+5.5°C))=100.0g×4.18 J/g°C×5.5 °C
M=(100.0g×4.18J/g°C×5.5°C)/(0.385 J/g°C×51 °C)
=117.09 grams.
6 (a). From the equation 1 mole of methane gives out 890.4 kJ
There fore 2 moles give:
(2×890.4)/1= 1780.8 kJ
(b) 22.4 g of methane.
Number of moles= mass/ RFM
RFM=12 + 4×1
=16
No. of moles =22.4 g/16g/mol
=1.4 moles
Therefore 1.4 moles produce:
1.4 moles × 890.4 kJ/mol=
=1246.56 kJ
7. From the equation, 2 moles of aluminium react with ammonium nitrate to produce 2030 kJ
Number of moles = mass/RAM
Therefore 9.75 grams = (9.75/26.982) moles of aluminium.
=0.3613 moles.
If 2 moles produce 2030 kJ, then 0.3613 moles produce:
(0.3631 moles×2030 kJ)/2
=368.55 kJ
8. From the equation, 4 moles of ammonia react with excess oxygen to produce 905.4 kJ of energy.
Number of moles= mass/molar mass
RMM= 14+3×1= 17
Therefore 0.5113 grams of ammonia = (0.5113 g/17g/mole) moles
= 0.0301 moles
If 4 moles produce 905.4 kJ, then 0.0301 moles produce:
(0.0301 moles×905.4 kJ)/4 moles
=6.81 kJ
9. From the equations, one mole of methane produces 890 kJ of energy while one mole of propane produces 2043 kJ.
Lets change 5.5 grams into moles of either alkane.
Number of moles= Mass/RMM
For propane, number of moles= 5.5g/ 44.097g/mol
=0.125 moles
For methane number of moles =5.5 g/ 16g/mol
=0.344 moles
0.125 moles of propane produce:
0.125 moles×2043 kJ/mol
=255.375kJ
0.344 moles of methane produce:
0.344 moles× 890 kJ/mol
= 306.16kJ
Therefore, 5.5 grams of methane produces more heat than 5.5 grams of propane.
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