Unit 18
Assignment A
Enthalpy inves.ga.on
Enthalpy change is when 1 mole of a substance reacts completely in oxygen when all reactants and
products are in their standard state. Enthalpy is used to determine if a reac=on was an endothermic
or exothermic reac=on, using enthalpy we are able to calculate the heat of reac=on of a chemical
process.
The equa=on for enthalpy change is as follows: H = U + PV
Enthalpy (H)
Internal energy (U)
Product of pressure (P)
Volume (V)
Entropy
Entropy is the distor=on of order in some amount of molecules, or the measure of randomness of
molecules in a system. An example of entropy is When a substance is heated, its energy rises (higher
enthalpy).
The molecules move quicker, which leads them to move in a less ordered manner, resul=ng in more
entropy than in their non-heated state.
To calculate the change in entropy, the equa=on is as follows:
Change in entropy = what you end up with – what you started with
The dissolving of anhydrous sodium carbonate in water
Equipment
- Polystyrene cup - S=rring rod
- 250 ml beaker
- Anhydrous sodium carbonate
- Dis=lled water
- Thermometer
- Weighing balance
- Clamp stand
- Measuring cylinder
, - Beaker
Method
1. A polystyrene cup was placed in a beaker to act as a stand.
2. 25 ml of dis=lled water was placed into a measuring cylinder, and was then poured into the
polystyrene cup.
3. The ini=al temperature of water was measured and recorded.
4. A weighing balance was used to weigh 4.1g of anhydrous sodium carbonate.
5. 4.1g of sodium carbonate was then carefully added into the polystyrene cup, the dis=lled
water and the anhydrous sodium carbonate was then s=rred using a s=rring rod.
6. The temperature change was then recorded every minute for 6 minutes.
7. The data that was recorded was then used to calculate the temperature change and was
then plo[ed into a graph.
Risk assessment
Anhydrous sodium carbonate does have a corrosive nature when it does contact the skin, if
anhydrous sodium carbonate was to get onto the skin it would cause severe irrita=on and poten=ally
blister and burn the skin, to mi=gate the risk gloves would have to be worn as that would act as a
barrier between the skin and the anhydrous sodium carbonate. Anhydrous sodium carbonate also
poses a risk if it was to enter the eyes, this would cause serious irrita=on and could poten=ally enter
the bloodstream through the eyes if it was accidentally rubbed into the eye. To reduce the risk of this
occurring safety goggles would have to be worn during the dura=on of the prac=cal to significantly
reduce the risk of injury.
The dissolving of ammonium chloride in water
Equipment
- Ammonium chloride (solid)
- Dis=lled water
- Beaker
- S=rring rod
- Thermometer
- Weighing balance
Method
1. A beaker was filled with 20ml of dis=lled water, the temperature of the water was taken
using a thermometer.
2. 5.3g of ammonium chloride was added into the beaker. The solu=on was then s=rred using a
s=rring rod.
Assignment A
Enthalpy inves.ga.on
Enthalpy change is when 1 mole of a substance reacts completely in oxygen when all reactants and
products are in their standard state. Enthalpy is used to determine if a reac=on was an endothermic
or exothermic reac=on, using enthalpy we are able to calculate the heat of reac=on of a chemical
process.
The equa=on for enthalpy change is as follows: H = U + PV
Enthalpy (H)
Internal energy (U)
Product of pressure (P)
Volume (V)
Entropy
Entropy is the distor=on of order in some amount of molecules, or the measure of randomness of
molecules in a system. An example of entropy is When a substance is heated, its energy rises (higher
enthalpy).
The molecules move quicker, which leads them to move in a less ordered manner, resul=ng in more
entropy than in their non-heated state.
To calculate the change in entropy, the equa=on is as follows:
Change in entropy = what you end up with – what you started with
The dissolving of anhydrous sodium carbonate in water
Equipment
- Polystyrene cup - S=rring rod
- 250 ml beaker
- Anhydrous sodium carbonate
- Dis=lled water
- Thermometer
- Weighing balance
- Clamp stand
- Measuring cylinder
, - Beaker
Method
1. A polystyrene cup was placed in a beaker to act as a stand.
2. 25 ml of dis=lled water was placed into a measuring cylinder, and was then poured into the
polystyrene cup.
3. The ini=al temperature of water was measured and recorded.
4. A weighing balance was used to weigh 4.1g of anhydrous sodium carbonate.
5. 4.1g of sodium carbonate was then carefully added into the polystyrene cup, the dis=lled
water and the anhydrous sodium carbonate was then s=rred using a s=rring rod.
6. The temperature change was then recorded every minute for 6 minutes.
7. The data that was recorded was then used to calculate the temperature change and was
then plo[ed into a graph.
Risk assessment
Anhydrous sodium carbonate does have a corrosive nature when it does contact the skin, if
anhydrous sodium carbonate was to get onto the skin it would cause severe irrita=on and poten=ally
blister and burn the skin, to mi=gate the risk gloves would have to be worn as that would act as a
barrier between the skin and the anhydrous sodium carbonate. Anhydrous sodium carbonate also
poses a risk if it was to enter the eyes, this would cause serious irrita=on and could poten=ally enter
the bloodstream through the eyes if it was accidentally rubbed into the eye. To reduce the risk of this
occurring safety goggles would have to be worn during the dura=on of the prac=cal to significantly
reduce the risk of injury.
The dissolving of ammonium chloride in water
Equipment
- Ammonium chloride (solid)
- Dis=lled water
- Beaker
- S=rring rod
- Thermometer
- Weighing balance
Method
1. A beaker was filled with 20ml of dis=lled water, the temperature of the water was taken
using a thermometer.
2. 5.3g of ammonium chloride was added into the beaker. The solu=on was then s=rred using a
s=rring rod.
