Which of the following are exothermic reactions?
(i) Burning of coal.
(ii) Reaction of water with quicklime.
(iv) Evaporation of water.
1)Burning of coal undergoes combustion reaction. Combustion reaction is a type of reaction in which chemical species experiences oxidation by undergoing a reaction with the oxidizing agent which results in the emission of energy in the form of heat. It is an exothermic process.
2)Quick lime is calcium oxide. It reacts with water to form calcium hydroxide. The reaction of water with quicklime releases a large amount of energy. Hence, this is an exothermic reaction.
3) Respiration is a series of exothermic reactions that occur in the mitochondria of living cells in order to release energy from food molecules. This energy can then be used to produce heat, for movement, growth, reproduction and active uptake.
Evaporation is endothermic because water molecules must absorb heat from the surroundings to increase their kinetic energy.Only evaporation of water is an endothermic reaction.
In the balanced equation
a Fe2O3 + b H2 → c Fe + d H2O
The values of a, b, c and d are the respectively:
The balanced reaction can be written as follow:
Fe2O3 + 3H2 → 2Fe + 3H2O
a→1, b→3, c→2, d→3.
Carbon dioxide turns lime water milky due to the formation of:
Ca(OH)2(aq) + CO2 → CaCO3(s) + H2O
Lime turns water turns milky
When a solution of barium chloride in water is added to an aqueous solution of sodium sulphate, the following happens:
When barium chloride solution is added to sodium sulphate solution, then a white precipitate of barium sulphate is formed along with sodium chloride solution.
BaCl2 (aq) + Na2SO4(aq) → BaSO4 (s) + 2NaCl(aq)
The process of reduction involves ______.
The process of reduction involves gain of electrons.
In the reaction: 3MnO2 + 4Al → 3Mn + 2Al2O3
The oxidising agent is:
MnO2 loses oxygen and therefore, gets reduced. Hence, it acts as an oxidising agent.
When magnesium ribbon is burnt in air, the ash formed is:
Ash is white powder of magnesium oxide.
The gas produced on addition of dilute sulphuric acid on powdered zinc is:
Zn + H2SO4(dil) → ZnSO4 + H2
When in the blue solution of copper sulphate, zinc strip is dipped, after some time the colour changes to:
Zn + CuSO4(aq) → Cu + ZnSO4
In the reaction: SO2(g) + 2H2S(g) → 2H2O(l) + S (s)
The reducing agent is:
H2S gets oxidised and hence it is a reducing agent.
A white precipitate can be formed when dil H2SO4 is added to aqueous solution of:
BaCl2(aq) + H2SO4(aq) → BaSO4(s) + 2HCl(aq)
When a solution of barium chloride in water is added to an aqueous solution of sodium sulphate, the following happens :
BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)
The formula of rust is:
Rust is Fe3O3. x H2O
In the double displacement reaction between aqueous potassium iodide and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate?
Pb(CH3COO)3 + 3KI → PbI3 + 3CH3COOK
Which one of the following four metals would be displaced from the solution of its salt by other three metals ?
Silver because it is the least reactive among these metals.
Which is the reducing agent in the reaction ?
ZnO + C → Zn + CO
C gets oxidised to CO and hence is a reducing agent.
The values of a, b, c and d in the balanced chemical equation, a BaCl2 + b Al2(SO4)3 → c AlCl3 + d BaSO4 are:
3BaCl2 + Al2(SO4)3 → 2AlCl3 + 3BaSO4
The formulae of quick lime and limestone are respectively:
Quick lime is CaO and limestone is CaCO3.
............ is a process in which there is loss of electrons.
Oxidation is a process that involves the loss of electrons.
Which of the following statements about the given reaction are correct?
3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
(i) Iron metal is getting oxidised
(ii) Water is getting reduced
(iii) Water is acting as reducing agent
(iv) Water is acting as oxidising agent
The substance which oxidises the other substance is called oxidising agent. So, water is an oxidising agent.