Unformatted text preview: Click to edit Master subtitle style We measure quantities of Heat using a Calorimeter . What we actually measure are masses and temperature changes. The Heat Capacity (C) of a system is the heat required to change the temperature of a system by 1 °C (or 1 K). Molar Heat Capacity is the Heat Capacity of 1 mole of a substance, Specific Heat Capacity is the Heat Capacity of a 1g sample of the substance. C = q / ΔT q = m × specific heat capacty × ΔT We can carry out reactions at constant pressure in a Coffee Cup Calorimeter , and measure qp (which is the same as ΔH). If we carry out reactions involving gases in a Bomb Calorimeter (which has a constant volume) we measure qv, (which is the same as ΔU from ΔU = q + w where w = –PΔV). We could calculate ΔH (which is more useful because our combustion reactions in the real world take place at constant P) from ΔU (from ΔH = ΔU + PΔV), however in most reactions (except those involving large volumes of gases) PΔV is small, and so essentially ΔH = ΔU. reactions (except those involving large volumes of gases) PΔV is small, and so essentially ΔH = ΔU....
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- Spring '08