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level: 6.3 Measuring enthalpy changes

Questions and Answers List

level questions: 6.3 Measuring enthalpy changes

Question	Answer
What are 3 examples of a simple calorimeter?	1. Polystyrene drinking cup 2. A vacuum flask 3. Metal can
What is specific heat capacity, c	Energy required to raise the temperature of 1g of a substance by 1*C (1K) is called specific heat capacity,c, of the liquid
The energy transferred as heat is given by what relationship	q = mc△T q = heat transferred in J m = mass of water in g c = Specific heat capacity in J g^-1 C^-1 △T = temperature change in C
Heat transferred for known number of moles of reactants in the calorimeter is given by?	q = mc△T
We can scale this up to get the enthalpy change per mole of defined reactant or product. Relationship we then use is	△H = -mc△T
A rise in temperature is given by a (positive / negative ) sign	positive
△H is negative for an (exo / endo ) reactions	exothermic
A fall in temperatures is given by a (positive / negative ) sign	negative
△H is positive for (exo / endo ) reaction	endothermic
What is the procedure for enthalpy change of neutralisation by experiment? ?50cm^3 of 1.0 mol dm^-3 hydrochloric acid ?50cm^3 of 1.0 mol dm^-3 sodium hydroxide	1. Place hydrochloric acid in cup and record its temperature. 2. Add sodium hydroxide (at room temperature) to acid in cup 3. Stir the reaction mixture with the thermometer and record highest temperature
To find the standard enthalpy change of combustion we need to know: (4)	1. mass of fuel burnt 2. Temperature rise of the water 3. mass of the water 4. relative molecular mass of the fuel (propan-1-ol).