Energetics

Question 1

what are exothermic reactions

Answer 1

Exothermic reactions = reactions that release energy to the surroundings

Question 2

what are endothermic reaction

Answer 2

Endothermic reactions= reactions that absorb energy from the surroundings

Question 3

what are the latin for endo exo and thermic

Answer 3

Thermic = heat
Exo = out
Endo = in

Question 4

what are some examples of exothermic reactions (4)

Answer 4

Examples of exothermic reactions:
BURNING - combustion reactions - in combustion something reacts with oxygen
2. Metals reacting with acid
3. Neutralisation reactions
4. displacement reactions -
5. Calcium Oxide and Water - it releases so much heat that it causes the water to boil and become steam. Calcium hydroxide (slaked lime) is produced

Question 5

what is formula for calcium oxide called

Answer 5

CaO = quicklime

Question 6

what is the formula for calcium hydroxide

Answer 6

Ca(OH)2 =slaked lime

Question 7

how do you slake quicklime

Answer 7

adding water = slaking it

Question 8

what is the displacement reaction between aluminium and iron (III)

Answer 8

2Al + Fe2O3 —> 2Fe + Al2O3

Question 9

what is enthalpy change

Answer 9

In a reaction, you can measure the enthalpy change, which is the amount of heat energy that is absorbed or released in a reaction

Question 10

what is the symbol for enthalpy change

Answer 10

The symbol for enthalpy change is Delta (triangle) H –> the delta means change

Question 11

can you have enthalpy on its own

Answer 11

You cannot have enthalpy on its own, you can only have enthalpy change

Question 12

what is the uni for enthalpy change

Answer 12

The unit for enthalpy change is kJ/mol - think of it as the amount of energy change per mol of reactant

Question 13

describe the energy change diagrams for endothermic

Answer 13

check starred msgs

Question 14

describe the energy change diagrams for exothermic

Answer 14

check starred msgs

Question 15

what is BENDOMEX

Answer 15

BENDOMEX
Breaking is ENDO, Making is EXO

Question 16

how dooes bonds relate to the energy absorbed/released in a reaction

Answer 16

in a reaction, the bonds between atoms are broken down, and then new bonds are made to create new compounds
When breaking bonds, energy is required, so energy is absorbed INTO the reaction, so you see the energy in the reaction profile increase
When making the bonds, energy is released OUT of the reaction, so you see the energy of the reaction go down.

Question 17

what is and whats an exmaple of endothermic reaction

Answer 17

An endothermic reaction is one where the heat energy is absorbed from the environment
An example of endothermic reaction is thermal decomposition (breaking a compound down using heat)
copper carbonate –> copper oxide + carbon dioxid

Question 18

what is a common source of error in enthalpy change expirements

Answer 18

The largest source of error in this experiment is the large amounts of heat loss to the surroundings

Question 19

what are some common sources of heatloss in an enthalpy change experiment

Answer 19

Sources of heat loss:
Warm water gives out some heat to the air
The open flame of the spirit burner transfers some heat to the air surrounding it as opposed to heating the water
Heat is also used to increase the temeprature of the copper can and the thermometer instead of the water

Question 20

why does unintended heatloss hinder an enthalpy change experiment

Answer 20

These factors can result in an incorrect value of enthalpy change obtained from the reading

Question 21

why is incomplete combustion a problem for enthalpy change experiements (2)

Answer 21

We are using the mass of ethanol as a factor for how much energy is being used
In this assumption, we rely on the fact it is ALWAYS releasing energy via complete combustion
HOWEVER, if there is insufficient oxygen, incomplete combustion would take place, which is a problem as incomplete combustion releases less energy than complete

Question 22

what is specific heat capacity

Answer 22

Specific heat capacity - the amount of energy, needed for 1g of a substance to get hotter by 1degrees celsius

Question 23

what is the equation for enthalpy change

Answer 23

Q = m x c x (delta)T

Question 24

what is Q in the enthalpy change equatiom