Energetics

Question 1

Thermometer not to touch base?

Answer 1

In contact with heat directly;

Temp higher than expected

Question 2

Why extinguish spirit lamp when temp rise to 5 degree

Answer 2

Higher change in temp
-> too much of the fuel needs to be burned
=> add significantly to exp time
=> more heat lost

Question 3

Why reweight the spirit lamp immediately?

Answer 3

• fuel is volatile, easily evaporate

- > reading inaccurate…

Question 4

How to improve exp?

Answer 4

Graphical method

-> compensates for heat loss by reaction mixture to the surrounding

Question 5

When explain the graph, what are the two things to explain?

Answer 5

1. Increasing parts
2. explain constant/ slight decreases
   - all the acid has reacted

Question 6

Why total volume kept constant?

Answer 6

• rise in temp is proportional to increase in energy pxed;

- any change in v gives diff change in temp for same energy pxed

Question 7

Why when heating, crucible is more suitable than boiling tube?

Answer 7

Wider SA for volatile sub to escape more readily;

Lower the risk of breakage due to condensation;

Withstand high temp;
Reduces risk of breakage

Question 8

How to record the measurement?

Answer 8

Mass of empty BT

Mass of BT& sample b4 heating

Mass of BT& sample after heating

Mass of sample used;

Mass loss

Question 9

Why experimental value < theoretical value

Answer 9

1. Incomplete combustion of ethanol due inadequate O2 supply, forming CO and C
   - > H2O2 that decomposes itself to supply O2
2. Mass of ethanol inaccurate
   - continue to evaporate
   - >cap the wig