Answer:
1) Minimum mass of methane required to heat 45.0 g of water by 21.0°C is 0.0788 g.
2) Minimum mass of methane required to heat 50.0 g of water by 26.0°C is 0.108 g.
Explanation:
1) Minimum mass of methane required to raise the temperature of water by 21.0°C.
Mass of water = m = 45.0 g
Specific heat capacity of water = c = 4.18 J/g°C
Change in temperature of water = ΔT = 21.0°C.
Heat required to raise the temperature of water by 21.0°C = Q
Q = 3,950.1 J = 3.9501 kJ
According to reaction 1 mole of methane on combustion gives 802.3 kJ of heat.
Then 3.950.1 kJ of heat will be given by:
Mass of 0.004923 moles of methane :
0.004923 mol × 16 g/mol=0.0788 g
Minimum mass of methane required to heat 45.0 g of water by 21.0°C is 0.0788 g.
2) Minimum mass of methane required to raise the temperature of water by 26.0°C.
Mass of water = m = 50.0 g
Specific heat capacity of water = c = 4.18 J/g°C
Change in temperature of water = ΔT = 26.0°C.
Heat required to raise the temperature of water by 21.0°C = Q
Q = 5,434 J= 5.434 kJ
According to reaction 1 mole of methane on combustion gives 802.3 kJ of heat.
Then 5.434 kJ of heat will be given by:
Mass of 0.006773 moles of methane :
0.006773 mol × 16 g/mol= 0.108 g
Minimum mass of methane required to heat 50.0 g of water by 26.0°C is 0.108 g.