Unit 8 Flashcards
(13 cards)
1
Q
- State the equation for calculating energy released from a fuel.
A
E=cmΔT
2
Q
- What is the term ‘c’ and what is its value?
A
specific heat capacity of water = 4.18
3
Q
- What is the term ‘mw’ and what are the units?
A
mass of water in kg
4
Q
How do you convert from cm3 to kg for water?
A
divide by 1000
5
Q
- What are the units of energy, Eh?
A
kJ (kilojoules)
6
Q
- Name two fuels studied in this topic.
A
ethanol and propanol
7
Q
- What is an exothermic chemical reaction?
A
a reaction that releases heat to the surroundings
8
Q
- What is an endothermic chemical reaction?
A
A reaction that rakes in heat from the surroundings
9
Q
- Are combustion reactions exothermic or endothermic?
A
exothermic
10
Q
- What does a fuel react with in a combustion reaction?
A
oxygen
11
Q
- Write a balanced chemical equation for the combustion of butanol.
A
C4H9OH + 6O2 → 4CO2 + 5H2O
12
Q
- If 50 cm3 of water increases in temperature from 22oC to 74oC when a spirit burner heats it, what is the Enthalpy change for this reaction
A
E=0.05 x 4.18 x 52
=10.9kJ
13
Q
State two reasons why the experimental value for enthalpy of combustion may be lower than the value found in a data booklet?
A
loss of heat to the surroundings
incomplete combustion
