Chemical Reaction

To determine the value of , we need to balance the given chemical reaction: Unbalanced equation: C₃H₈ + O₂ → CO₂ + H₂O
Step 1: Balance carbon (C) atoms There are 3 carbon atoms in C₃H₈, so we need 3 CO₂ molecules: C₃H₈ + O₂ → 3CO₂ + H₂O
Step 2: Balance hydrogen (H) atoms There are 8 hydrogen atoms in C₃H₈, so we need 4 H₂O molecules: C₃H₈ + O₂ → 3CO₂ + 4H₂O
Step 3: Balance oxygen (O) atoms On the right side, total oxygen atoms = 3 × 2 (from CO₂) + 4 × 1 (from H₂O) = 6 + 4 = 10 So, we need 5 O₂ molecules on the left side to get 10 oxygen atoms: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

The correct option is (D):

When lead nitrate reacts with potassium iodide, a double displacement reaction occurs. The products formed are lead iodide (PbI ) and potassium nitrate (KNO ). Lead iodide is insoluble in water and forms a bright yellow precipitate. This yellow color is characteristic of solid PbI , and none of the other reactants or products are yellow.

The correct option is (C): Pbl

The given chemical equation is:
BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl

In this reaction:
- Barium (Ba²⁺) from BaCl₂ combines with SO₄²⁻ from Na₂SO₄ to form BaSO₄ (a precipitate).
- Sodium (Na⁺) and Cl⁻ ions combine to form NaCl.

This is a classic example of a double-displacement reaction, where ions are exchanged between the reacting compounds.

The names of the sub-shells present in M shell (n = 3) are 3s, 3p, 3d.

✅ Correct answer: 3s, 3p, 3d

Explanation: For a given principal quantum number n, the possible sub-shells are determined by the azimuthal quantum number l, which can take values from 0 to (n − 1).
So, for n = 3:
→ l = 0 → 3s
→ l = 1 → 3p
→ l = 2 → 3d
Hence, the sub-shells are 3s, 3p, and 3d.

The colour of methyl orange in an alkaline medium (basic solution) is yellow.

✅ Correct answer: yellow

In acidic medium, methyl orange appears red, and in basic (alkaline) medium, it turns yellow.

The chemical name of baking soda is sodium hydrogen carbonate. It has the chemical formula NaHCO₃. It is commonly used in baking, cleaning, and as an antacid.

✅ Correct answer: sodium hydrogen carbonate

Acetic acid ( ) is a weak organic acid. It partially dissociates in water to release ions, making it a weak acid.

It does not act as a base under normal conditions.

Final Answer: is a , which corresponds to option .

Ore-Formula Matching:

• : This is magnetite, a common iron ore. Thus, matches with .
• : This is magnesite, a magnesium carbonate mineral. Thus, matches with .
• : This is zinc blende, a zinc sulfide mineral. Thus, matches with .
• : This is cinnabar, a mercury sulfide mineral. Thus, matches with .

Correct Matching:

Final Answer: The correct option is , which corresponds to the matching: .

The balanced chemical equation is: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

First, let's find the molar masses of the relevant substances:

• Molar mass of CaCO₃ = 40.08 (Ca) + 12.01 (C) + 3 x 16.00 (O) ≈ 100 g/mol
• Molar mass of HCl = 1.01 (H) + 35.45 (Cl) ≈ 36.5 g/mol
• Molar mass of H₂O = 2 x 1.01 (H) + 16.00 (O) ≈ 18 g/mol

From the balanced equation, the stoichiometric ratio is: 1 mole of CaCO₃ reacts with 2 moles of HCl to produce 1 mole of H₂O. In terms of mass: 100 g of CaCO₃ reacts with 2 x 36.5 g = 73 g of HCl to produce 1 x 18 g = 18 g of H₂O. This confirms the information given in the first part of the problem.

Now, consider the second case where 300 g of CaCO₃ and 146 g of HCl are used. We need to find the limiting reactant.

Convert the given masses to moles:

• Moles of CaCO₃ = 300 g / 100 g/mol = 3.0 mol
• Moles of HCl = 146 g / 36.5 g/mol = 4.0 mol

Determine the limiting reactant based on the stoichiometric ratio (1 mole CaCO₃ : 2 moles HCl):

• To react completely with 3.0 mol of CaCO₃, we need 3.0 x 2 = 6.0 mol of HCl. We only have 4.0 mol of HCl.
• To react completely with 4.0 mol of HCl, we need 4.0 / 2 = 2.0 mol of CaCO₃. We have 3.0 mol of CaCO₃, which is more than enough.

Therefore, HCl is the limiting reactant.

The amount of product (H₂O) formed is determined by the amount of the limiting reactant (HCl). From the balanced equation, 2 moles of HCl produce 1 mole of H₂O.

Calculate the moles of H₂O produced using the moles of the limiting reactant (HCl): Moles of H₂O = (4.0 mol HCl) x (1 mol H₂O / 2 mol HCl) = 2.0 mol H₂O

Convert the moles of H₂O to grams: Mass of H₂O = Moles of H₂O x Molar mass of H₂O Mass of H₂O = 2.0 mol x 18 g/mol = 36 g

The correct option is (B): 36

The given unbalanced chemical equation is: To balance this equation, let's first balance the hydrogen atoms. The left side has 1 hydrogen atom from , and the right side has 2 hydrogen atoms in . Therefore, we need 2 molecules on the left side to balance the hydrogen atoms: Next, balance the oxygen atoms. On the left side, we have 2 oxygen atoms in , so we need 2 molecules on the right side to balance the oxygen atoms:

The correct option is (C):

Let's analyze each option:

Rusting of Iron: This is a chemical process because iron reacts with oxygen and water to form iron oxide (rust).
Changing water into water vapour: This is a physical process, not chemical, as it involves a change in the state of matter (from liquid to gas) without changing the chemical composition of water.
Mixing metal acid and base: This is a chemical process where a reaction occurs between the metal, acid, and base, resulting in the formation of products.
Baking a cake: This is a chemical process, as it involves chemical reactions (like the formation of new compounds and the release of gases) during baking.

Thus, the correct answer is changing water into water vapour, as this is a physical change, not a chemical change.

The correct option is (B): Changing water into water vapour

An oxidizing agent is a substance that causes another substance to undergo oxidation, which means the other substance loses electrons. In the process, the oxidizing agent itself undergoes reduction, meaning it gains electrons.

Oxidation refers to the loss of electrons, while reduction refers to the gain of electrons.
The oxidizing agent facilitates the oxidation of another substance and is itself reduced.

Thus, the correct answer is that the oxidizing agent oxidizes another substance and undergoes reduction itself.

The correct option is (D): It oxidizes other substance and itself undergoes reduction

Roasting is a process where ores are heated in the presence of oxygen, usually to remove sulfur or other impurities. Among the given options:
Carbonate ores usually undergo calcination, which involves heating the ore in the absence of air to decompose it and remove carbon dioxide.
Oxide ores are often reduced by heating in the presence of a reducing agent.
Sulphide ores undergo roasting, where they are heated in the presence of oxygen to convert them into oxides, releasing sulfur dioxide gas.

The correct option is (C): Sulphide ores