Federal Board Class X Chemistry

SECTION “A”

Q.1. Insert the correct option.

i. Electricity can pass through matter sodium chloride because of the presence of

• Free electrons
• Moveable ions
• Moveable atoms
• Sodium metal

ii. If sulphuric acid in contact with dry blue litmus paper, it will

• Turn yellow
• Turn green
• Turn red
• Remain unchanged

iii. What happens when one mole of methane is mixed with four moles of Chlorine in the dark at room temperature

• There is no reaction
• CH₃Cl and HCl are formed
• CCl₄ and HCl are formed
• Carbon and HCl are formed

iv. The process which results in the weakening of the attraction between particles is called

• Condensation
• Freezing
• Crystallisation
• Evaporation

v. What is the color of the flame when Hydrogen burns

• Golden yellow
• Blue
• Crimson
• Green

vi. What is the general formula used for alkynes?

• CnH₂n₊
• CnH₂n
• CnH₂n₊₂
• CnH₂n₋₂

vii. In which is the solubility of grease is greater?

• Alcohol
• Water
• Benzene
• Common salt solution

viii. What would be the weight of three moles of sodium hydroxide?

• 60g
• 80g
• 100g
• 120g

ix. Which of the following acids may be used with sodium hydrogen carbonate for the fermentation of wheat flour

• Benzoic acid
• Carbonic acid
• Citric acid
• Hydrochloric acid

x. If the molecule AX₃ is polar and obeys the octet rule: what pair of electrons would the central atom A have?

• No electron pair
• One electron pair
• Two bond pairs and one electron pair
• Only bond pairs and one electron pair

xi. Which of metals is extracted from the ore ‘Limonite’?

• P₂O₅
• MnO₂
• V₂O₅
• Fe₂O₃

xii. Which of the following have a good solubility in a solvent of great polarity?

• Covalent compound
• Ionic compound
• Neutral compound
• All of them

xiii. Which of the bonds are in order to decreasing ionic characters?

• F – F, F – H, Cs – F
• F – F, Cs – F, H – H
• Cs – F, F – F, H – F
• Cs – F, H – F, F – F

xiv. On an industrial scale, nitric acid is prepared y reacting

• Nitrogen with Oxygen
• Ammonia with air
• Ammonium nitrate with sodium chloride
• Nitrogen per oxide with air

xv. In which of the following is Silicon not present?

• Cl₂ + 2Nal → 2NaCl + l₂
• Br₂ + 2NaCl → 2NaBr + Cl₂
• Cl₂ + 2NaBr → 2NaCl + Br₂
• Br₂ + 2Kl → 2KBr + l₂

SECTION “B”

Q.2. Attempt all the questions.

i. The chemical formula NH₄NO₃ represents the compound ammonium nitrate

(a) How many atoms of nitrogen are shown in the formula?
(b) What is the relative formula mass of the compound?
(c) Calculate the percentage by mass of nitrogen in ammonium nitrate.

ii. Complete the table by naming the products formed when the following substances are electrolyzed using inert electrodes

Substance ………………. Product formed at cathode ………….. Product formed at anode
Dilute Sulpharic acid
Fused Sodium Chlorine
Aqueous Sodium Chlorine

iii. Doctor has advised Bilal to take milk of magnesia as a treatment for his stomachache

(a) Write down the formula for the medicine
(b) Write a balanced equation for the reaction of this medicine in the stomach

iv. (a) Name the particle produced when Brylium “Be” is bombarded with alpha particles.
(b) Write down the equation on the reaction
(c) What is the charge on the particle?
(d) Give the mass of the particle.

v. A catalyst benzoyl peroxide is used in the preparation of plastic

(a) What is the name of polymer?
(b) Write the equation for its preparation.
(c) Give one property and one used of this polymer.

OR

A porous mass obtained from water glass is kept in the medicine bottles to absorb moisture readily

(a) Name the substance
(b) How water glass is prepared
(c) Write down any one use of water glass.

vi. The element chlorine (Atomic number = 17) is a mixture of two isotopes Cl³⁵ and Cl³⁷.

(a) State the number of neutron and protons in both isotopes.
(b) Justify that 1 mole of Chlorine gas has a mass of 71 grams.
(c) Draw the atomic models of both isotopes.

vii. Phosphoric acid (H₃PO₄) reacts with calcium hydroxide (Ca(OH)₂) to produce water and calcium phosphate (Ca₃(PO₄)₂

(a) Write a balanced chemical equation for the reaction.
(b) Find out the mass of calcium hydroxide required to react completely with 30g of phosphoric acid.
(c) Find out the amount of calcium phosphate produced in this reaction.

xiii. Consider the following elements

Hydrogen, Magnesium, Sulphur Neon

(a) Which of the above mentioned elements burns in oxygen forming an acidic oxide?
(b) Which of these elements is used in the manufacture of ammonia?
(c) Which of these elements produce basic oxides on oxidation?

ix. Chlorine is an oxidation agent. Write down the equations of the reaction of Chlorine with

(a) Aqueous Potassium Bromide
(b) Hot and concentrated solution of Caustic soda
(c) Carbon monoxide
(d) Sulphuric Acid

x. (a) How can hardness of water be removed by the use of sodium carbonate?

Give the equation of the chemical reaction involved.

(b) Which compound soda ash obtained from and how?
(c) How can we prepare carbon dioxide from sodium carbonate?

xi. Explain why?

(a) Metals are good conductor of electricity.
(b) High pressure changes the shapes of metals.
(c) The melting point of magnesium metal is higher than sodium metal.

xii. Hydrochloric acid solution when added to a beaker containing sodium hydroxide solution heats up the beaker.

(a) Name the type of reaction which takes place when the two solutions are mixed.
(b) What is the reason behind the heating up of the beaker.
(c) Name the spectator ions in the mixture.

SECTION “C”

Q.3. Crude oil extracted from earth’s crust a mixture of different hydrocarbons

(a) How can these compounds be separated?
(b) Which principle is involved in the separation of these fractions?
(c) Describe the details of Carbon composition of different fractions.

OR

Sulphur is found in free state under the earth’s surface.

(a) How is extracted by the Frasch-method?
(b) Sulphur can be used as a raw material in the manufacture of sulphuric acid by contact process. Write down the main steps involved in the process.

Q.4. (a) There are certain indications by which we can say that a chemical reaction is taking place.

i. State at least four of these indications.

ii. Which chemical reaction takes place when lime reacts with carbon dioxide?

iii. Which reaction is used in the laboratory to produce insoluble salts? Give at least one example.

Q.4. (b) i. Keeping in mind the Aufbau Principle, write down the electronic configuration of the elements

Fluorine
Argon
Calcium
Carbon

Q.4. (b) ii. Calculate the number of moles of sulphuric acid required to prepare 400 cm³ of 6M sulphuric acid solution.

Q.5. (a) State Mendeleev’s Periodic Law.

What were the defects in it? How was the periodic law modified to remove these defects?

Q.5. (b) What is co-ordinate covalent bond?

How is this bond different from a covalent bond? Explain your answer by giving an example.

Q.6. (a) Oxidation and reduction are two opposite processes. Differentiate between them by giving appropriate chemical reactions.

Q.6. (b) Write down the composition of Brass and Bronze.