Energetics

Question 1

For an endothermic reaction what sign will the enthalpy change have?

Answer 1

Positive +

Question 2

For an exothermic reaction what sign will the enthalpy change have?

Answer 2

Negative -

Question 3

In an endothermic reaction the temperature _____________
And in an exothermic reaction the temperature _____________

Answer 3

Decreases
Increases

Question 4

Q =

Answer 4

mcΔT

Question 5

ΔH=

Answer 5

Q / n

Question 6

In terms of bonds broken and bonds made ΔH =

Answer 6

Bonds broken - bonds made

Question 7

Describe the method of combustion calorimetry.

Answer 7

Weigh out 50g of water and place in a can above the burner
Measure the initial mass of the burner and the initial temperature of the water
Ignite the burner, stir water for 30 seconds, the extinguish the burner
Measure the final mass of the burner and the final maximum temperature of the water.

Question 8

Why do we measure the initial and final mass of the burner?

Answer 8

To calculate the mass burnt for the equation to find moles

Question 9

What are the two significant sources of error in the combustion calorimetry experiment?

Answer 9

Heat loss - most of the heat energy dissipates into the air instead of water
Incomplete combustion - releases less energy than expected

Question 10

Describe the method to conduct a solution calorimetry experiment.

Answer 10

Pipette 25cm3 of CuSO4 into a polystyrene cup
Measure the initial temperature of the solution
Add 1g of Mg and stir continuously
Measure the max temp of the solution

Question 11

What are the potential sources of error for solution calorimetry?

Answer 11

Heat loss, incomplete reaction, water being heated is no longer pure water as it has things dissolved in it which would mean it doesn’t have the same specific heat capacity anymore.