(1) (a) and (b)
(2) (a) and (c)
(3) (a) (b) and (c)
oxidation is gain of oxygen and reduction reaction is released of oxygen
(a) and (b)
QUESTION 10 Fe2O3 + 2Al -> AL2O3+ 2Fe
The above reaction is an example of a
Solution: (d) displacement reaction
QUESTION 11 What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct Solution.
(a) Hydrogen gas and iron chloride are produced.
(b) Chlorine gas and iron hydrochloric are produced.
(c) No reaction takes place.
(d) Iron salt and water are produced.
Solution: (a) Hydrogen gas and iron chloride are produced.
What is a balance chemical equation? Why chemical equation should is balanced?
Solution: A chemical equation is balanced when the number of atoms of each type involved in a chemical reaction are same on both the reactant and product sides of the equation.
According to the law of conservation of mass, when a chemical reaction occurs, the mass of the products should be equal to the mass of the reactants. Therefore, the amount of the atoms in each element does not change in the chemical reaction. As a result, the chemical equation that shows the chemical reaction needs to be balanced. A balanced chemical equation occurs when the number of the atoms involved in the reactants side is equal to the number
QUESTION 13 Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia
(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
(c) Barium chloride reacts with aluminum sulphate to give aluminum chloride and a precipitate of barium sulphate
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
How to solve these type of question
(a) 3H2 +N2 -> 2NH3
(b) 2H2S + 3O2 -> 2H2O + 2SO2
(c) 3BaCl2 + Al2 (SO4)3 -> 2AlCl3 + 3BaSO4
(d) 2K + 2H2O -> 2KOH + H2
QUESTION 14. Balance the following chemical equation.
(a) HNO3 + Ca(OH)2 -> Ca(NO3)2 +H2O
(b) NaOH + H2SO4 -> Na@SO4 + H2O
(c) NaCl + AgNO4 -> AgCl + NaNO#
(d) BaCl2 + H2SO4 -> BaSO4 + HCl
How to solve these type of question
a) 2HNO3 + Ca(OH)2 -> Ca(NO3)2 + 2H2O
(b) 2NaOH + H 2SO4 -> Na2SO 4 + @H 2O
(c) NaCl + AgNO 3 -> AgCl + NaNO 3
(d) BaCl 2 + H 2SO 4 -> BaSO 4 + 2HCl
QUESTION 15: Write the balance chemical equation for the following reaction.
(a) Calcium hydroxide +Carbon dioxide -à Calcium carbonate + Water
(b) Zinc + Silver Nitrate -à Zinc Nitratew + Silver
(c) Aluminium +Copper chloride -à Aluminium Chloride + Copper
(d) Barium chloride + Potassium sulphate -à Barium Sulphate + Potassium chloride.
How to solve these type of question
(a) Ca(OH02 + CO 2 -> CaCo 3 +H 2O
(b) Zn + 2AgNO 3 -> Zn(NO 3) 3 + 2Ag
(c) 2Al + 3CuCl 2 -> 2AlCl 3 + 3Cu
(d) BaCl 2 +K 2SO 4 -> BaSO 4 +2KCl
QUESTION 16 Write the balance chemical equation for the following and identify the type of reaction in each case.
(a) Potassium bromide (aq) + Barium iodide(aq) -à Potassium iodide(aq) + Barium bromide(s)
(b) Zinc carbonate(s) -à Zinc oxide(s) + Carbon dioxide(g)
(c) Hydrogen (g) + chlorine(g) -à Hydrogen chloride(g)
(d) Magnesium (s) + Hydrochloric acid (aq) -à Magnesium chloride(aq) +Hydrogen (g)
Solution: (a) 2KBr(aq) + BaL2 -> 2KL(aq) + BaBr 2(s), Double displacement reaction.
(b) ZnCO 3 (s) -> ZnO(s) + CO 2 Decomposition reaction.
( c) H 2(g) +CL 2 (g) -> 2HCL(g) Combination reaction.
QUESTION 17 What does one mean by exothermic and endothermic reaction? Give examples.
Reaction in which heat is released along with the formation of product are called exothermic reaction. Example of exothermic reaction are-
Burning natural gas : CH 4 +2O 2 (g) -> CO 2(g) + 2H 2O (g)
Reaction in which energy is absorbed are known as endothermic reaction. Example of endothermic reaction are :
2AgBr(s) sun light- -> 2Ag(s) +Br 2 (g)
The key point is heat is absorbed in the process. Endo means energy is absorbed
QUESTION 18: Why is respiration considered an exothermic reaction ? explain.
The steps to respiration are
Step 1 :Food that we eat includes carbohydrates, proteins etc.
Step 2: During digestion , carbohydrates are broken down in simpler substances called glucose.
Step 3: Glucose combines with oxygen in the cells of our body to provide energy.
This reaction is called respiration. Since energy is releases during this process, respiration is an exothermic reaction.
C 6H 12O 6 (aq) + 6O 2(g) -> 6CO 2(aq) +6H 2O(i) + Energy
QUESTION 19: Why are decomposition reactions called the opposite of combination reaction ? Write equation for these reactions.
When a single substance decomposes to give two or more substances .It is called decomposition reaction
The generalized reaction for chemical decomposition is:
Decomposition reaction: AB + Energy -> A+ B
Example: CaCO 3(s)Heat-- -> CaO(s) + CO 2(g)
When reaction two or more substances combine to form a new single substance
Combination reaction: A +B -> AB + energy
Example: Burning of coal: C(s) + O 2(g) --à CO 2(g)
So it is clear that Decomposition reaction are opposite of combination reactions.
QUESTION 20: Write one equation each for decomposition reaction where energy is supplied in the form of heat , light or electricity.
We already know that When a single substance decomposes to give two or more substances .It is called decomposition reaction
So examples are
CaCO 3(s) - -> CaO(s) + CO 2(g)
2AgBr(s) -> 2Ag(s) + Br 2(g)
2H 2O(I) -> 2H 2 + O 2(g)
QUESTION 21: What is the difference between displacement and double displacement reaction ? Write equation for these reactions.
A displacement reaction
It is chemical reaction in which a more reactive element displaces a less reactive element from its salt solution.
Example: Fe + CuSO 4 - -> FeSO 4 +Cu
In this reaction , one displacement is taking place. Fe is displacing Cu
Double displacement reaction
It is a chemical reaction in which there is an exchange of ions between the reactants to give new substances. There are two displacements taking place in a double displacement reaction.
Example: 3BaCL 2 + AL 2 (SO 4) 3 - -> 2ALCl 3 +3BaSO 4
In these reaction two displacements is taking place. Ba is displacing AL and AL is displacing Ba
QUESTION 22: In refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reactions involved.
2 agNO 3(aq) + Cu(s) -> Cu(NO 3) 2 + 2Ag(s)
QUESTION 23 What do mean by precipitation reaction? Explain by giving example.
Important points are
1)Any reaction that produces a precitate can be called a precipitation reaction.
2) Precipitation reaction produce insoluble salts which settle down as precipitate.
For example : When aqueous sodium sulphate solution and aqueous barium chloride are reacted, aqueous solution of sodium chloride and white precipitate of barium sulphate are formed.
Na 2SO 4(aq) + BaCL 2(aq) -> BaSO 4(s) + 2NaCL(aq)
QUESTION 23: Explain the following in terms of gain or loss of oxygen with two examples each.
Oxidation is the gain of oxygen.
Example 1: ZnO + C -> Zn + CO
In this reaction , ZnO is getting reduced to Zn and C is getting oxidized to CO. Therefore the conversion of ZnO is reduction and the conversion of C to CO is oxidation.
Reduction is the loss of oxygen.
Example2: CuO +H 2 -> Cu + H 2O
IN this reaction , CuO is getting to Cu and H 2 is getting oxidized to H 2O. Therefore, the conversion of CuO is reduction and the conversion of H 2 to H 2O is oxidation.
QUESTION 24: A shiny brown coloured element “X” on heating in air becomes black in colour. Name the element “X” and the black coloured compound formed.
Solution: The element “X” is copper and the black coloured compound is copper oxide (CuO). The chemical reaction is :
2Cu + O 2 - -> 2CuO
QUESTION 25: Why we do apply paint on iron articles?
Iron react with air and moisture and corrode .So we apply paint on iron articles to avoid rusting of iron. Paint will stop the contact of air and moisture with iron.
QUESTION 26: Oil and fat containing food items are flushed with nitrogen. Why?
Solution: When fats and oil are oxidized , they become rancid and their smell and taste change. Food items containing fat and oil are flushed with nitrogen to prevent rancidity of oil and fat as nitrogen is an inert gas and prevent the oxidation of oil and fats.
QUESTION 27: Explain the following terms with one example each.