Test: Chemical Reactions & Equations - Class 10

Balanced Equation:
H₂ + Cl₂ → 2HCl₂

The above reaction is an example of combination reaction because two different elements are combining to form a single compound.

Option C is a double displacement reaction. Na will displace Ag and combine with NO₃ to form NaNO₃. Ag will then combine with Cl and form AgCl. So the products of the reaction are AgCl and NaNO₃.

Fe + CuSo₄ → FeSO₄ + Cu 
is displacement reaction.
In these reaction iron (Fe) displaces copper (Cu) 
Hence, it is a displacement type of reaction.

(a) is a decomposition reaction.
(b) and (d) are neutralisation reactions.

Balanced equation:
H₂ + 2Cl₂ → 2HCl₂

The above reaction is an example of combination reaction. 

A decomposition reaction occurs when one reactant breaks down into two or more products. Examples of decomposition reactions include the breakdown of hydrogen peroxide to water and oxygen, and the breakdown of water to hydrogen and oxygen.
2KClO₃ → 2KCl + 3O₂

An oxidizing agent oxidizes other substances and gains electrons; therefore, its oxidation state decreases. Hence, it gets reduced.

Oxidation reaction which produce heat and light is called combustion. Here, when we burn petrol in the presence of Oxygen, it produces heat and light which proves that it is a combination reaction.

So option C is the correct answer. 

Balanced chemical equation: A balanced equation is a chemical equation in which number of atoms of each element is equal on both sides of the equation i.e number of atoms of an element on reactant side = number of atoms of that element on the product side.

ZnO(s) + CO(s) → Zn(s) + CO₂(g)

• Since oxygen has combined with carbon, carbon is the one that is oxidized and ZnO is the oxidizing agent. Similarly carbon has taken the oxygen of ZnO, carbon is the reducing agent and ZnO is the one that has been reduced.
• Reducing agent-C
• Oxidizing agent-ZnO
• Oxidized-CO
• Reduced- ZnO

​​​​​​​So Option C is correct

C + O₂  → CO₂ + Heat

• This is a Combination reaction because C and O₂ are combining to produce one single compound CO₂.
• This is also an Oxidation reaction because carbon is getting oxidized.
• This is also an exothermic reaction because in this reaction heat is getting released.

​​​​​​​So Option D is correct

• In the given reaction, the compound breaks down into two simpler products.
• Calcium carbonate is decomposed to calcium oxide and carbon dioxide.

​​​​​​​So Option A is correct

Fe₂O₃ + 2Al → Al₂O₃ + 2Fe
This reaction is an example of a displacement reaction.
Here, Aluminum is more reactive metal than Fe. Therefore, Al will displace Fe from its oxide.

​​​​​​​So Option D is correct

• In the reaction SO₂ is getting reduced to S as oxygen is being removed.
• Similarly, H₂S is oxidised to S as hydrogen is removed.
• The species getting oxidised facilitates the reduction process and is the reducing agent.
• Hence, H₂S is the reducing agent and Oxidising agent is SO₂.

So, option B is correct

An element X exposure to moist air, forms a reddish brown and a new compound Y is formed. 
Fe + H₂O +O₂  →  Fe₂ O₃ 
This Fe₂O₃ is the reddish brown compound which is called rust. 
So , X → Fe 
Y →  Fe₂O₃

​​​​​​​So Option A is correct

• Hydrogen gas and iron chloride are produced.

Fe + HCl →  FeCl₂  + H₂

• The iron displaces hydrogen from hydrochloric acid to form iron (II) chloride & hydrogen gas. This is a single displacement reaction.
• Thus the answer is option (A) Hydrogen gas and iron chloride are produced.

Fe(s) + CuSO_4​ ⟶ Cu(s) + FeSO_4​

When an iron nail is dipped in copper sulphate solution, a brown coating of copper is formed on the surface of iron and the colour of copper sulphate solution changes from blue to light green. This reaction shows that iron is more reactive than copper as it displaces copper from its solution and iron passes into solution as Fe²⁺ ions and ferrous sulphate solution is formed.

​​​​​​​So Option D is correct

Copper sulphate aqueous solution is blue in colour .

​​​​​​​So Option D is correct

The correct option is B

silvery

Explanation for correct option

(B) The color of Zinc metal is silvery.

• An electron gets excited to a higher energy � orbital from a lower energy d orbital. The frequency of light absorbed is proportional to the excitation energy.
• This frequency is usually in the visible range.
• The color seen corresponds to the complementary color of the light absorbed.
• Zinc (Zn) is a bluish-silvery metal.

Hence, option (B) is correct. The color of Zinc metal is silvery.

A burning splinter since hydrogen gas burns with a pop sound.

Zinc being an active metal readily reacts with hydrochloric acid at room temperature to form soluble zinc chloride and hydrogen.

Zn + 2HCl → ZnCl₂ + H₂.

​​​​​​​So Option C is correct

• No we can't store copper sulphate in an iron vessel.
• Iron is more reactive than copper and it will displace copper from its sulphate solution.
• If we store it, the iron pot will get destroyed.
• Copper Sulphate solution cannot be stored in an Iron container because iron is more reactive than copper, therefore a reaction will take place.
• Fe+CuSO₄ = FeSO₄+Cu

So Option C is correct.

To prevent rusting:

• The iron articles should be painted, the machine parts should be oiled or greased, galvanized iron pipes are used for water supply.
• But ( iron articles should be covered with plastic) is the incorrect method of preventing rusting. 

​​​​​​​So Option B is correct

It is a bright yellow odourless crystalline solid, that becomes orange and red when heated. It was formerly called plumbous iodide.

​​​​​​​So Option D is correct

An oxidizing agent, or oxidant, gains electrons and is reduced in a chemical reaction. Also known as the electron acceptor.

The process of changing water vapour into water is called condensation. It is not a chemical reaction.

When milk converts in curd the process is irreversible and a new substance with different properties is formed hence it is an example of a chemical change.

Rusting of iron is also a chemical change.

2Na + 2H₂O → 2NaOH + H₂ 

A balanced equation is an equation for a chemical reaction in which the number of atoms for each element in the reaction and the total charge are the same for both the reactants and the products.

So Option B is correct