Federal Board Class X Chemistry

SECTION “A”

Q.1. Insert the correct option.

i. In phlogistan theory, when a substance is burnt, the phlogiston escapes into air. What is the thing left behing?

• Iron pyrite
• Royal water
• Calx
• Calcinations

ii. When a solution of Copper Sulphate is treated with magnesium metal. What will happen to the blue colour or copper sulphate?

• Turn pink
• Discharged
• Turn light pink
• No changes

iii. An atom is like a positively charged ball studded with negatively charged electrons at some places.

• Bohr’s atomic model
• Rutherford atomic model
• Hund’s model
• Plum pudding model

iv. A very small unit of length used to measure the atomic radius as 10⁻⁹ part of a meter is called?

• Nanometer
• Millimeter
• Picometer
• None

v. Which one of the molecule / ions give below has the highest polarity between atoms.

• H – Cl
• 0 – H
• CO₂
• H – H

vi. In winter sea water is frozen forming an ice layer which floats over water. Beneath it aquatic animals enjoy their life. This happens because the ice layer behave as

• Good coductor of heat
• Bad conductor of heat
• Partially conductor of heat
• None of these

vii. Solute ions surrounded by solvent molecules in a solution are called solvated ions. If the solvent is water, these ions are called hydrated ions. What will this process be called?

• Hydrated
• Hydrolysis
• Hydration
• Salvation

viii. In an acid base titration using phenolphthalein as an indicator, we observe light pink colour at one stage. What does it indicate?

• Reaction will be completed in a while
• Reaction is proceeding
• Reaction is completed
• Reaction is just started

ix. What is the best and cheapest method for sterilization of water that is also most effective in destroying pathogenic bacteria?

• Boiling water
• Clark’s method
• Ion exchange method
• Chlorination

x. Tyres are used in automobiles. They are usually black in colour and stiff. What is the substance that gives them such properties?

• Rubber
• Activated charcoal
• Carbon Black
• Carbon wood

xi. Carbon monoxide is very dangerous for health and causes suffocation. This happens when absorption of oxygen in blood is hindered. What causes this hindrance?

• Carbon monoxide itself
• Carboxy hemoglobin
• Carboxy carbon monoxide
• Hemoglobin

xii. Gold and platinum are not dissolved even in all the strong acids, except in aqua regia which is a 3 : 1 mixture of HCl and HNO₃. What is that gives aqua regia this solubilty?

• Chlorine gas formation
• Greater amount of HCl
• Formation of soluble ions
• Formation of soluble chlorides

xiii. The transition temperature between two allotropes of sulphur is 96°C. Which two allotropes does it refer to

• Rhombic sulphur and monoclinic sulphur
• Monoclinic sulphur and plastic sulphur
• Rhomobic sulphur and plastic sulphur
• Plastic sulphur and needle like sulphur

xiv. Lodized table salt helps to prevent goiter. This iodized salt is obtained mixing table salt with

• 0.002% Potassium iodide
• 0.02% Potassium iodide
• 0.02% Potassium chloride
• 0.025% Potassium chloride

xv. What is the process called when roasted ore is melted in the blast furnace along with mixture of coal and sand?

• Roasting
• Jugging
• Smelting
• Skimming

xvi. When Ethyne is passed through a red hot iron tube, benzene is formed. What is the reaction called?

• Polymerization
• Combustibility
• Monomerization
• Halogenations

xvii. There are different methods for preservation of food. One of them is preservation by radiation. What are the most suitable rays used for it?

• Alpha rays
• Helium nuclei
• Gamma rays
• Beta rays

SECTION “B”

Q.2. Attempt any FOURTEEN parts. (42)

i. Diatomic hydrogen is a gas. It can react with different compounds to form products. Write balanced equations along with conditions for the preparation of following products form hydrogen:

Phosphine
Methyl Alcohol
Ethane

ii. Silicone is found in nature in combined form as silicon dioxide and silicate mineral.

a. Draw the linkage of methyl silicone polymer
b. Write the reaction of silicone dioxide with calcium phosphate
c. Write names of two naturally occurring crystalline forms of silicone dioxide.

iii. The binary compounds (oxides) of oxygen on the basis of the valence number of oxygen are classified into different groups.

a. Write names of their main oxides
b. Give two examples of oxides, where valance number of oxygen is – 1/2

iv. Free Sulphur can exist in several allotropes. Heat has remarkable effect on Sulphur changing one allotropes into other.

a. Name the allotropes of Sulphur
b. What happens when molten Sulphur is heated?
c. When molten Sulphur is poured into cold water, which allotrope is formed?

v. Ammonia is manufactured by reaction between nitrogen and hydrogen. These two gases are compressed to 200 atmospheric pressure at 400-500°C.

a. Write the equation including state symbols for the formation of Ammonia.
b. If nitrogen gas used in above reaction is prepared in laboratory, write suitable reactions for its preparation by the downwards displacement of water.

vi. Formation of different colours of precipitate in chemical reaction indicate presence of different compounds or ions. Similarly the halides are also confirmed by the colour of their precipitates.

a. Write suitable chemical reactions for preparations of each, which can differentiate between all the halides formed.

vii. Aluminum is extracted from Alumina by Hall’s process.

a. Write the principle of the process.
b. Write chemical reactions occurring in the process.
c. What are the functions of molten cryolite in the process.

viii. Methane is a major component of natural gas. It is also called marsh gas because it is found in marshy places.

a. How is methane prepared in laboratory from Sodium Ethanoate?
b. It is not affected by acids or alkalis in laboratory under normal conditions, why?
c. Discuss and draw structure of methane.

ix. Empirical formula is also called the simplest formula Sand is represented by an empirical formula SiO₂.

a. Draw the structure of SiO₂.
b. If the empirical formula of compound is CH₂O, its molecular mass is 60. c.What will be its molecular formula?
d. Name the molecular compound.

x. Chemistry is as sold as the history of mankind on earth. This modern era of chemistry is dependent on the period of scientific advancement in early period and Islamic period.

a. Give the concept of Aristotle?
b. Explain the formulation given by Gibbs.
c. What work was done by Abu-Rehman Muhammad Al-Beruni?

xi. The number of sub-shells present in a shell is equal to its principal quantum number (n).

a. Give the number of sub-shells in n=4 and also name those sub-shells.
b. Give the formula which gives the maximum number of electrons in any energy level.
c. Give increasing order of the energy of the sub-shells belonging to different shells.
d. Give another name of a sub-shell.

xii. Many theories and concept about an acid and bases.

a. Give Lewis concept about an acid and base.
b. Write a chemical equation which indicates the formation of a co-ordinate covalent bond between Lewis acid and Lewis base.
c. The sting of honey bee is acidic, whereas the sting of wasp is alkaline. What first aid will you provide to the affected persons of both insects?

xiii. Electro Chemical series is the list of ions arranged in the order of their ease of discharged at the electrode.

a. If a solution contains a mixture of ions, how will you find out, which ion will be discharged first and which will be discharge at the end by the help this series.
b. How is the basic principle for discharging of ions in Electro chemical series deviated by the nature of the Cathode material used.

xiv. The concentration of a solution can be expressed in different ways.

a. How is it expressed using percentage by volume? Give example.
b. Determine the amount of sodium carbonate (Na₂CO₃) required to prepare 200cm³ of M/2 solution. Molar mass of Na₂CO₃ is 106.

xv. Physical and chemical properties of elements gradually change in group sand periods.

a. What trend is shown by atomic radii in periods?
b. Give reasons in support of your above answer.
c. Define electron affinity. Give its trend in any period.

xvi. With the help of chemical equations explain Clark’s method for the removal of temporary hardness of water.

xvii. Give at least six points (Postulates) of ionic theory.

xviii. Define unsaturated hydrocarbons. How are they classified? Define each class and explain with the help of example.

SECTION “C”

NOTE: Attempt any TWO questions. (26)

Q.3. Iron is extracted from its ores. Blast furnace is used for this purpose.

(a) Draw labeled diagram of the blast furnace.
(b) How is carbon monoxide used as reducing agent in this process? Write all chemical reactions with carbon monoxide in this regard.
(c) What is slag? How is it produced in this process? Give reactions.
(d) Give the name of iron obtained from blast furnace.
(e) How is nitric acid prepared in industry by Ostwald’s method? Explain with the help of chemical reactions.

Q.4. (a) State vital force theory and give preparation reaction of urea.
(b). Define isomerism, give isomers of butane.
(c). Identify the given functional groups: – COOH , – OH , C – X
(d). Define law of multiple proportions and give one example in its support.
(e). 35g of lime stone (CaCO₃) react with an excess of hydrochloric acid according to the given equation. How many moles and grams of calcium chloride with be produced?
CaCO₃ + 2HCl CaCl₂ + HO + CO₂
(Ca=40, C=12, O=16, Cl=35.5, H = 1)

Q.5. (a) How are atoms arranged in metal and how can the shape of a metal be changed? Explain giving diagram.
(b). Define hydrogen bonding. Name the atoms involved in this bonding and explain why they are involved? Give example of water and hydrogen fluoride.
(c). Define a solution, identify solute and solvent present in the given solutions.

i. Hydrogen gas absorbed in palladium.
ii. Carbon particles in air.
iii. Ally as (Pb + Sn)
iv. Alcohol in water.

(d). Give postulates of Bohr’s atomic model.
(e). Define law of triads and give example.