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When Every Child Matters!

The Global Classroom carries the unique GEMS “Dynamic” materials and assessments of Dr Sunita Gandhi, Ph.D. Cambridge University, UK. These have been tested and tried in three countries, Iceland, India and the UK, and perfected with a three year trial with over 40,000 children in India participating.

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Covering Chapters
1.	Relative Molecular Mass and Mole	12.	Preparation, Manufacture, Properties and Uses of Compounds
2.	Nuclear and Radio Chemistry	13.	Types of Chemical Reactions and their Mechanisms
3.	Chemical Bonding	14.	Ethers
4.	States of Matter: Structure and Properties (The Solid State)	15.	Aldehydes and Ketones
5.	Phase Rule	16.	Carboxylic Acids and Acid Derivatives
6.	Chemical Kinetics	17.	Glycine
7.	Ionic Equilibria	18.	Organic Compounds Containing Nitrogen
8.	Electrochemistry	19.	Carbohydrates
9.	Chemical Energetics	20.	Aromatic Compounds (Benzene and its Derivatives)
10.	Extraction, Properties and Uses of Metals	21.	Polymers
11.	Isolation, Manufacture, Properties and Uses of Non-Metals	22.	Isomerism

Questions

Question 2 (a)		[2]
(1)	Why is the freezing point of a liquid depressed when a non-volatile solute is dissolved in it?

Question 2 (a)		[2]
(2)	Calculate the amount of ice that will separate out on cooling a solution containing 50 g of ethylene glycol in 200g of water to –9.80C. [Kf(H2O)=1.86 K kg mol–1]

Question 2 (b)		[2]
Select the bombarding projectile for each of the following :
(i)
(ii)

Question 2 (c)		[1]
(1)	BF3 has three polar (B–F) bonds although BF3 molecule is non-polar. Why?

Question 2 (c)		[1]
(2)	What is the kind of hybridisation in a carbon atom with two p–bonds?

Question 2 (c)		[1]
(3)	Water has bent structure, although the hybridization of central oxygen atom is sp3. Why?

Question 3 (a)		[1]
(1)	Mention a difference between crystalline and amorphous solids.

Solutions Tips and Guidelines

Solution :
(b)	In a pure liquid the whole surface of the liquid is occupied by the molecules of the liquid whereas in case of a solution containing a non-volatile solute the number of molecules of the liquid at the surface of the solution decrease. This reduces the escaping tendency of the solvent molecules thereby lowering vapour pressure of the liquid. So the freezing point of the liquid decreases as freezing point is directly related to vapour pressure.
Formulae/Tips :
(i)	Non-volatile solute has no vapour pressure of its own.
(ii)	On entering the intermolecular spaces of a solvent it reduces its vapour formation capacity by decreasing the exposed surface area.
(iii)	Dtf is lowering in V.P. of solvent.
(iv)	By definition, freezing point of a liquid is that temperature at which solid and liquid forms of the substance have the same vapour pressure.

•	The MAXIM Classbook

•	GEMS Dynamic Assessments

•	PerBooks Personalised TopicBooks

•	Sure Success Series

•	TargetPLUS On-Line Mocks

•	UK GCSE Mock Papers for Mathematics

•	GEMS “Dynamic” at a Glance

•	Philosophy Behind GEMS “Dynamic”

•	GEMS “Dynamic” Surveys and Perbooks

•	GEMS “Dynamic” Reports

•	GEMS “Dynamic” Training

•	GEMS “Dynamic” Lab School?