An iron bar of mass 841 g cools from 84°C to 7°C. Calculate the heat released (in kilojoules) by the metal.

28.75211 kj

Explanation:

Given data:

Mass of iron bar = 841 g

Initial temperature = 84°C

Final temperature = 7°C

Heat released = ?

Solution:

Specific heat capacity:

It is the amount of heat required to raise the temperature of one gram of substance by one degree.

specific heat capacity of iron is 0.444 j/g.°C

Formula:

Q = m.c. ΔT

Q = amount of heat absorbed or released

m = mass of given substance

c = specific heat capacity of substance

ΔT = change in temperature

ΔT = 7°C - 84°C

ΔT = -77°C

By putting values,

Q = 841 g × 0.444 j/g.°C × -77°C

Q = 28752.11 j

In Kj:

28752.11 j × 1 kJ / 1000 J

28.75211 kj

the answer would be c

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.