Test Session Chapter 4 Stoichiometry (9th Smart Syllabus)

Multiple Choice Questions 10×1=10

1 Which is the correct formula of calcium phosphide?

A CaP

B CaP₂

C Ca₂P₃

D Ca₃P₂

2 Methane gas is represented by:

A CH₄

B N₂

C NaCl

D O₃

3 Formula of common salt is:

A NaCl

B PH

C HCl₃

D CaCl₂

4 Formula of Aluminum Oxide is:

A Al₂O₃

B Al₃O₂

C AlO

D Al₃O₃

5 What is the correct chemical formula for the binary compound formed between carbon and oxygen?

A CO

B CO₂

C C₂O

D C₂O₂

6 Who is credited with the discovery of Avogadro’s number?

A Amedeo Avogadro

B Jacques Charles

C Joseph Gay-Lussac

D Robert Boyle

7 How many grams of O₂ are present in 2 moles of O₂?

Hint: Molar mass of O₂ = 32 g/mol

A 32g

B 132g

C 64g

D 128g

8 What is mole in chemistry?

A A unit of mass

B Unit of volume

C Unit of amount of substance

D None of these

9 What type of chemical reaction involves the combination of two or more substances?

A Synthesis

B Replacement

C Neutralization

D None of these

10 40 g of H₃PO₄ contains number of moles?

Hint: Molar mass of H₃PO₄ = 98 g/mol

A 0.58g

B 4.8g

C 0.408g

D 5.8g

Short Answer Questions 15×2=30

I Write down the chemical formulas of the following compounds: Calcium phosphate, Aluminium nitride, Sodium acetate, Ammonium carbonate and Bismuth sulphate. Constructed Response

Ca₃(PO₄)₂ · AlN · CH₃COONa · (NH₄)₂CO₃ · Bi₂(SO₄)₃

II Why does Avogadro’s number have an immense importance in chemistry? Constructed Response

III Different compounds will never have the same molecular formula but they can have the same empirical formula. Explain Constructed Response

IV What is meant by binary ionic compounds?

V Give four examples of binary ionic compounds.

VI What is the significance of a chemical formula?

VII What is the structural formula of sulphuric acid?

H — O — S — O — H
‖
O

VIII What is meant by the structural formula?

IX Who is Amedeo Avogadro?

X Differentiate between reactants and products.

xi What is the number of moles of O₂ required to burn 2 moles of methane? CH₄ + 2O₂ → CO₂ + 2H₂O

CH₄ + 2O₂ → CO₂ + 2H₂O

xii What is balanced chemical equation?

xiii What is Haber’s process?

xiv Give two examples of the compounds which have same empirical and molecular formulas. Exercise

xv Write down the names of three such compounds which have different empirical and molecular formulas. Exercise

Detailed Answer Questions (Answer any 2) 2×5=10

1 Explain the concepts of Avogadro’s number and mole.

Key Points: Avogadro’s number = 6.022 × 10²³ particles/mol, Mole concept, Relation to atomic/molecular mass

1 mole = 6.022 × 10²³ particles = Molar mass in grams

2 How to write a chemical formula?

3 How many molecules of water will be produced if we react 5g of hydrogen gas with excess of O₂ gas?

2H₂ + O₂ → 2H₂O

Calculation Steps:
1. Molar mass of H₂ = 2 g/mol
2. Moles of H₂ = mass/molar mass
3. From stoichiometry: 2 moles H₂ → 2 moles H₂O
4. Number of molecules = moles × Avogadro’s number