Exothermic reactions: "Exo" relates to external, or outside, and "thermic" means heat. Some examples of exothermic reactions include combustion (burning), oxidation reactions (rusting) and neutralization reactions between acids and alkalis

Q = m × c × ΔT
Q is the energy transferred in joules, m is the mass of the substances in kg, c is the specific heat capacity in J/kg degrees C, and ΔT is the temperature change in degrees C in the specific heat formula.
Heat Released Calculator
Imagine 100 g of an acid was mixed with 100 g of an alkali, which resulted in the temperature increase from 24 degrees C to 32 degrees C.
The equation for a neutralization reaction between an acid and an alkali can be reduced to:
H⁺ + OH^- --> H2O

The formula to use: Q = mc ∆T

Mass = m = 100 g + 100 g / 1000 g per kg = 0.2 g (one significant figure)
Specific heat capacity of water = c = 4,186 J/kg degrees C
Change in temperature = ΔT = 24 degrees C - 32 degrees C = -8 degrees C
Q = (0.2 kg) (4,186 J/kg degrees C) (-8 degrees C )
Q = -6,688 J, which means 6,688 joules of heat is released.

Hydrogen (H2)	120-142 MJ/kg
Methane (CH4)	50-55 MJ/kg
Methanol (CH3OH)	22.7 MJ/kg
Dimethyl ether - DME (CH3OCH3)	29 MJ/kg
Petrol/gasoline	44-46 MJ/kg
Diesel fuel	42-46 MJ/kg
Crude oil	42-47 MJ/kg
Liquefied petroleum gas (LPG)	46-51 MJ/kg
Natural gas	42-55 MJ/kg
Hard black coal (IEA definition)	>23.9 MJ/kg
Hard black coal (Australia & Canada)	c. 25 MJ/kg
Sub-bituminous coal (IEA definition)	17.4-23.9 MJ/kg
Sub-bituminous coal (Australia & Canada)	c. 18 MJ/kg
Lignite/brown coal (IEA definition)	<17.4 MJ/kg
Lignite/brown coal (Australia, electricity)	c. 10 MJ/kg
Firewood (dry)	16 MJ/kg
Natural uranium, in LWR (normal reactor)	500 GJ/kg
Natural uranium, in LWR with U & Pu recycle	650 GJ/kg
Natural uranium, in FNR	28,000 GJ/kg
Uranium enriched to 3.5%, in LWR	3900 GJ/kg

Coal is a mixture of inorganic mineral matter (the stuff that becomes ash when coal is burned) and carbonaceous matter (carbon containing structures). To take information from the “Users Handbook for the Argonne Premium Coal Samples” (1993) one of the 6 samples in the collection is a coal from the Illinois coal basin, named Illinois #6. It is a high sulfur-containing bituminous coal. The analysis of the Illinois #6 coal (in dry %) is 77.7% C, 5% H, 13.5% oxygen, 4.83% sulfur and 15.5% ash. An “empirical formulae” is sometimes calculated for coals, this is simply taking the organic material in the coal and determining the number of atoms of each in relation to 100 atoms of carbon. So for this Illinois #6 an “empirical formulae” was determined based on the analysis of the elements found in the carbonaceous material of the coal. It ended up as C100 H77.3 O13.1 N1.5 S1.2.

A spirit burner was filled with ethanol (C₂H₅OH) and used to heat a copper can containing 200 cm³ of water. The temperature of the water rose from 22˚C to 27˚C.

Calculate the heat energy released from this combustion of ethanol.
All of the values for this equation are either known constants c or available in the question (m and ΔT)
c = the specific heat capacity of water = 4.18 kJ kg^-1 ˚C^-1
m = the mass of water in kg so 200 cm³ = 0.2 kg
ΔT = the change in temperature = 27 - 22 = 5˚C
Eh=cmΔT=4.18×0.2×5=4.18kJ

The amount of energy released on complete combustion of 1250 g of coal, if its calorific value is 30kJ/g, is

The correct option is A
37.5×106 J
Mass of coal, m = 1250 g

Calorific value =30kJ/g=30×103J/gCalorific value =Em⇒E=m×Calorific value⇒E=1250×30×103 J=37.5×106 J

Hence, the correct answer is option (a).