Types of Reaction
Why is it necessary to balance a chemical equation?
Chemical equation must be balanced so as to
follow the law of conservation of mass.
Given the following observations:
Metal A displaces metal B from its salt solution.
Metal B does not displace metal D from its salt solution.
Metal C displaces metal B from its salt solution.
Arrange metals A, B, C, and D in decreasing order of reactivity.
Based on the reactions:
A displaces B → A > B
C displaces B → C > B
B does not displace D → B < D
So:
A > C > B > D
A colourless liquid ‘X’ has a pH of 2.5, turns blue litmus red, reacts with zinc to release a gas, and conducts electricity. What can you infer about substance X?
A. It is a weak acid because it reacts with zinc.
B. It is a strong acid and releases hydrogen gas on reaction with metal.
C. It is a base that forms hydrogen gas with zinc.
D. It is neutral because it conducts electricity.
B. It is a strong acid and releases hydrogen gas on reaction with metal.
Which oxide will turn blue litmus solution to red?
A. SO2
B. MgO
C. Na2O
D. NO2
a) A and D b) B and C
c) A and C d) All of these
a) A and D
“I’m a chemistry dance, a swap of fate,
Where one gains shine, the other sheds weight.
I make metals rust and fires flare,
You’ll find me in cells with energy to spare.
What am I?”
👉 Answer: Redox Reaction
State the type of chemical reactions:
Ammonia and hydrogen chloride gases are mixed.
NH3 (g) + HCl(g) -----> NH4Cl(s);
Combination reaction
A grey-colored metal X reacts with a blue-colored solution of compound Y and turns the solution colorless. A brown layer is deposited on metal X.
a) Identify metal X and compound Y.
b) Which species is oxidized and which is reduced? Justify your answer.
Metal X = Zinc (Zn)
Compound Y = Copper(II) sulphate (CuSO₄)
Zinc is oxidized: Zn → Zn²⁺ + 2e⁻
Copper(II) ion is reduced: Cu²⁺ + 2e⁻ → Cu
Justification: Zinc loses electrons (oxidation), Copper gains electrons (reduction).
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Surprise Question By Bevin Sir.
Which of the following substances when dissolved in equal volume of water, will have the highest pH value?
A. Sulphuric acid
B. Acetic acid
C. Magnesium hydroxide
D. Sodium hydroxide
D. Sodium hydroxide
“I live in your kitchen, but don’t get confused,
I’m not just a sour thing that salads have used.
I’m weak but I sting, my smell gives me fame,
In cleaning and science, I play a sharp game.
What acid am I?”
👉 Answer: Acetic Acid
Which of the following equations represent redox reactions and what are the
values for ‘p’ and ‘q’ in these equations?
Equation 1: Fe2O3(s) + 2Al(s) ----> Al2O3 (s) + p Fe(l) + heat
Equation 2: 2C4H10(g) + 13O2(g) --△--> 8CO2(g)+ q H2O(g)
A. Only equation 1 is a redox reaction, p =1 and q=3
B. Both equations 1 and 2 are redox reactions, p= 2 and q=4
C. Only equation 2 is a redox reaction, p= 2 and q= 10
D. Both equations 1 and 2 are redox reactions, p= 2 and q=10
D. Both equations 1 and 2 are redox reactions, p= 2 and q=10
An iron nail is added to each of the two test tubes ‘P’ and ‘Q’ containing aqueous copper (II) sulphate, and aqueous silver nitrate respectively. Which of the following observation is correct?
A. In test tube ‘P’ iron nail is coated with a blue coating and in test tube ‘Q’ there is no reaction.
B. Iron nail is coated with a brown coating in test tube ‘P’ and silver coating in test tube ‘Q’.
C. There is no reaction in either of the test tubes ‘P’ or ‘Q’.
D. There is no reaction in test tube ‘P’ but a silver coating on iron nail is seen in test tube ‘Q’.
B. Iron nail is coated with a brown coating in test tube ‘P’ and silver coatings in test tube ‘Q’.
Four statements about the reactions of oxides with dilute hydrochloric acid and aqueous sodium hydroxide are listed.
I. Aluminium oxide reacts with both dilute hydrochloric acid and aqueous sodium hydroxide.
II. Calcium oxide reacts with dilute hydrochloric acid and aqueous sodium hydroxide.
III. Zinc oxide reacts with both dilute hydrochloric acid and aqueous sodium hydroxide.
IV. Sulphur dioxide does not react with either dilute hydrochloric acid or aqueous sodium hydroxide.
Which statements are correct?
A. I and II
B. I and III
C. II and IV
D. III and IV
B. (I) and (III)
Methyl orange is added to dilute hydrochloric acid and to aqueous sodium hydroxide. What is the colour of the methyl orange in each solution?
Sample color | in dilute hydrochloric acid | colour in aqueous sodium hydroxide
A | Orange | Red
B | Red | Yellow
C |. Red | Orange
D | Yellow | Red
B. Red Yellow
“I burn without fire, yet I’m cool to the touch,
I clean up your grime, I’m used very much.
I can unclog, dissolve, and slip down the drain,
But don’t take me lightly — I cause chemical pain.
Who am I?”
👉 Answer: Caustic Soda (Sodium Hydroxide)
In the reaction of aqueous solution of barium chloride with aqueous solution of sodium sulphate, the aqueous solution formed will be:
A. BaCl2
B. BaSO4
C. Na2SO4
D. NaCl
D. NaCl
A redox reaction given below is used for the extraction of metals in its pure form from its oxide. Deduce the incorrect statement about the reaction among the given statements.
2PbO(s) + C(s) → 2Pb(s) + CO2(g)
Lead is getting oxidized
Carbon dioxide is getting reduced
Carbon gains oxygen atoms and gets oxidized
Lead present in lead oxide is reduced
(I) and (II)
(III) and (IV)
(I), (II) and (III)
All
2. (III) and (IV)
When excess of carbon dioxide is passed through lime water, the milkiness disappears because
A. water soluble calcium carbonate converts to water soluble calcium bicarbonate.
B. insoluble calcium carbonate converts to water soluble calcium bicarbonate.
C. water soluble calcium carbonate converts to insoluble calcium bicarbonate.
D. insoluble calcium carbonate converts to insoluble calcium bicarbonate.
B. insoluble calcium carbonate converts to water soluble calcium bicarbonate.
A student adds methyl orange to four unknown solutions. The colours observed are:
Solution A: Yellow
Solution B: Orange
Solution C: Red
Solution D: Faint pink
Which of the following is most likely true?
A. Solution A is a strong base, and C is a strong acid.
B. Solution B is a strong acid, and D is a strong base.
C. Solution A is neutral, and B is weak acid.
D. Solution C is a base because red indicates a change.
Methyl orange turns:
Red in acidic medium
Yellow in basic medium
Orange in weak acid or near neutral
Therefore:
A: Yellow → Strong base
C: Red → Strong acid
“I start as a powder, quite soft and dry,
Add me to water, and I harden nearby.
From sculptures to casts, I heal and create,
But heat me too far, and I change my state.
Who am I, used in mold and art’s gate?”
👉 Answer: Plaster of Paris
Wat type of reaction?
Quick lime reacts vigorously with water releasing
a large amount of heat.
Combination Reaction
Question:
Iron reacts with dilute hydrochloric acid to form iron(II) chloride and hydrogen gas:
Fe + 2HCl → FeCl₂ + H₂
Based on the reaction and your knowledge of redox reactions, which of the following statements is correct?
A. Iron is reduced because it forms Fe²⁺ ions.
B. Hydrogen ion (H⁺) is oxidized because it gains electrons.
C. Iron is oxidized as it loses electrons to form Fe²⁺ ions.
D. This is not a redox reaction because there is no oxygen involved.
C. Iron is oxidized as it loses electrons to form Fe²⁺ ions.
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Which of the following statements is true about the reaction between aqueous sodium hydroxide and hydrochloric acid?
A. It produces a basic salt and water.
B. It is a displacement reaction because ions are exchanged.
C. It is a redox reaction as H⁺ is reduced to water.
D. It is a neutralization reaction producing a neutral salt and water.
Correct Answer: D
“I’m neither food nor flame, yet I change hue with pride,
In acid I blush, in base I hide.
I don’t taste or fizz, but I still reveal,
The secret nature of what you conceal.
What chameleon am I in the chemist’s wheel?”
👉 Answer: Methyl Orange