give 10 ex of exothermic and endothermic change
Answers
Examples of exothermic reactions:
The burning or combustion of hydrocarbon fuels (see Oil Products) e.g. petrol or candle wax, these are very exothermic reactions.
The exothermic burning-combustion of fossil fuels is very important source of energy.
methane (natural gas) + oxygen ==> carbon dioxide + water (+ heat energy)
CH4 + 2O2 ==> CO2 + 2H2O
The burning of magnesium, reaction of magnesium with acids, or the reaction of sodium with water (see Metal Reactivity Series)
2Mg + O2 ==> 2MgO (+ heat energy)
Using hydrogen as a fuel in hydrogen-oxygen fuel cells (see Electrochemistry).
All these combustion reactions are oxidations.
Explosions are caused by VERY fast exothermic reactions producing very fast large expanding volumes of gases.
Metal displacement reactions are also exothermic. If you add iron filings to copper sulfate solution there is quite a temperature rise.
iron + copper sulfate ===> iron sulfate + copper
Fe(s) + CuSO4(aq) ==> FeSO4(aq) + Cu(s)
The neutralisation of acids with alkalis (see Acids, Bases and salts) e.g.
sodium hydroxide + hydrochloric acid ==> sodium chloride + water
NaOH + HCl ==> NaCl + H2O (+ heat energy)
Its the same for the neutralisation reactions between potassium hydroxide and sulfuric and nitric acids etc.
Other uses of exothermic reactions:
Hand warmers contain chemicals that when mixed together give out heat.
Self-heating cans of coffee, soup or hot chocolate have chemicals contained in the base of the container that when mixed generate enough energy to heat the contents of the can.
The Thermit reaction between aluminium powder and iron(III) oxide is VERY exothermic and when the mixture is ignited with a lit magnesium 'fuse' it goes off like a firework.
aluminium + iron(III) oxide ===> aluminium oxide + iron
2Al + Fe2O3 ===> Al2O3 + 2Fe
This is another example of a displacement reaction where a more reactive metal displaces a less reactive metal from one of its compounds.
This kind of reaction is used to extract certain metals from their purified ores.
Examples
Endothermic Reaction Examples
When ammonium chloride (NH4Cl) is dissolved in water, an endothermic reaction takes place. The salt dissociates into ammonium (NH4+) and chloride (Cl–) ions. The chemical equation can be written as follows: NH4Cl (s) + H2O (l) ⟶ NH4Cl (aq) – Heat
Ammonium nitrate (NH4NO3), an important component in instant cold packs, dissociates into the ammonium cation (NH4+) and the nitrate anion (NO3–) when dissolved in water. These ions go on to form ammonium hydroxide (NH4OH) and nitric acid (HNO3) respectively (by reacting with the OH– and H+ ions in water). This reaction is endothermic in nature since it cools the surroundings by absorbing heat from it.
The formation of nitric oxide from the reaction between nitrogen and oxygen is endothermic since it involves the absorption of approximately 180.5 kilojoules of heat for every mole of N2 and O2.
Other Endothermic Processes
The melting of ice to form water.
Evaporation of liquid water, forming water vapor.
Sublimation of solid CO2
The baking of bread.