C3.3 Energy Calculations
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Explain how a catalyst increases the rate of the reaction. [2]
• provides an alternative route - with a lower activation energy
Temperature before heating 20.7 °C Temperature after heating 35.1 °C Calculate the energy used to heat 50ml of water. Use the equation Q = m × c × ΔT The specific heat capacity of water = 4.2 J / g / °C [3]
35.1 - 20.7 = 14.4 [1] q = 50 x 4.2 x 14.4 = 3024[1] J [1]
Mass of spirit burner before ethanol was burned 72.80 g Mass of spirit burner after ethanol was burned 72.10 g Calculate the number of moles of ethanol (C2H5OH) that were burned. Relative atomic masses (Ar): H = 1; C = 12; O = 16
72.80 - 72.10 = 0.7g [1] 12+12+1+1+1+1+1+1+16=46[1] 0.7/46 = 0.015[1]
Explain why the incomplete combustion of methane is dangerous. [2]
Produces carbon monoxide (CO)[1] Which is poisonous [1]
Explain why, in terms of the energy involved in bond breaking and bond making, the combustion of methane is exothermic. [3]
energy is taken in / required to break bonds [1] energy is given out when bonds are made [1] the energy given out is greater than the energy taken in [1]