Viraf J. Dalal solutions for New Simplified Middle School Chemistry [English] Class 8 chapter 8 - Water [Latest edition]

Name a ‘pure form’ and an,‘impure form’ of water in the natural state.

State what is potable water. Give its qualities or characteristics which make it fit for human consumption.

Give a reason why water is called a ‘universal solvent’ but, an alkali is not.

Name the solute, solvent & solution in the statement – ‘sodium chloride dissolves in water to give sodium chloride solution’. Define each of the terms in italics.

Explain how the following factor affects the formation of a solution is proportion of the solute & the solvent.

Explain how the following factor affects the formation of a solution is particle size of the solute.

Explain how the following factor affects the formation of a solution is Temperature of the solvent.

Define the term ‘solubility ’ of a solute in water. If 10 g. of a solute is added to 100 g. of water at 50°C and stirred, it is seen that the total solute dissolves at that temperature giving an unsaturated solution. Is 10 g, the solubility of the solute in water. Give reasons.

Give a reason why alcohol and water form a miscible mixture while oil & water do not.

Give a reason why boiled water tastes flat.

Give a reason why on opening a bottle of soda [carbon dioxide dissolved in water] the gas escapes out with a ‘fizz’.

Give the importance of dissolved minerals & salts.

Give the importance of dissolved air – in water.

How are solutions generally classified. What is the basis of this classification.

Draw a table to differentiate – True solutions, colloidal solutions & suspensions – with respect to

1. Type of mixture
2. Solute particles in the mixture.

Give four examples of each of the above types of solutions i.e. true solution, colloidal solution & suspension. Give a reason why a true solution does not exhibit ‘Tyndall effect’.

If 5 g. of a solute is added to 50 ml. of a solvent at a particular temperature and the solution can dissolve more of the solute at that temperature – is the solution obtained a saturated or an unsaturated solution. Give reasons.

Explain the meaning of the term ‘saturated solution’. State two methods to convert a saturated solution to an unsaturated solution.

State how a ‘supersaturated’ solution differs from a ‘saturated solution’. State briefly how you would prepare a supersaturated solution using potassium chloride and water.

The process of separation or deposition of crystals from a hot saturated solution on gentle cooling of the solution is called ‘crystallization’. With reference to the statement explain what is meant by ‘water of crystallization. State which physical properties of a crystal are correlated with the water of crystallization.

Differentiate between ‘hydrated’ & ‘anhydrous’ crystals. Give the chemical formula of – the following hydrated crystals -

(a) Washing soda
(b) Gypsum
(c) Blue vitriol
(d) Epsom salt
(e) Glauber’s salt.
State which crystal from (a) to (e) is a pentahydrate.

Differentiate between an efflorescent, deliquescent & ‘ hygroscopic substance with suitable examples.

Differentiate the function of concentrated sulphuric acid as a drying agent & as a dehydrating agent. Is fused calcium chloride a dehydrating or a desiccating agent. Give reasons.

Give a reason why metals are arranged in a series called – ‘activity series of metals’. Name a metal which reacts with

(a) Cold water
(b) Boiling water
(c) Steam to liberate hydrogen in each case.

Differentiate between Hard & soft water with suitable examples.

Differentiate between Temporary & permanent hard water with suitable examples.

Give balanced equation to show how temporary hardness enters into water.

Give balanced equation to show how temporary hardness in water can be removed by boiling.

Give balanced equations to show how permanent hardness in water can be removed by addition of washing soda.

Select the correct answer of the following statement:

The medium of dissolution which allows the solute to dissolve in it.

Select the correct answer of the following statement:

A solution which can pass through a filter paper but not through a semipermeable membrane.

Select the correct answer of the following statement:

A decahydrate crystal.

Select the correct answer of the following statement:

A drying agent placed in desiccator.

Select the correct answer of the following statement:

A heterogenous mixture of undissolved particles in dispersion medium, visible to the naked eye.

Give a balanced equation for the following conversion:

Calcium sulphate in permanent hard water to calcium carbonate using sodium carbonate.

Give a balanced equation for the following conversion:

Iron to triiron tetroxide using steam.

Give a balanced equation for the following conversion:

Sulphur dioxide to sulphurous acid using a neutral liquid.

Give a balanced equation for the following conversion:

Potassium oxide to a strong alkali.

Give a balanced equation for the following conversion:

Magnesium bicarbonate in temporary hard water to magnesium carbonate by boiling.

Complete the statement by filling the blank with the correct word from the option.

Solubility of most solids ___ with rise in temperature.

Complete the statement by filling the blank with the correct word from the option.

Kerosene & water form a _______ mixture.

Complete the statement by filling the blank with the correct word from the option.

Solubility of a solute is the _______ amount of solute that will saturate 100 g. of water at t°C.

Complete the statement by filling the blank with the correct word from the option.

Hygroscopic substance absorb moisture from the atmosphere & _______their original state.

Complete the statement by filling the blank with the correct word from the option.

The ratio of hydrogen & oxygen in water is ____.

Give reason for the following:

All solutions are homogenous mixtures of a solute in a solvent.

Give reason for the following:

Hardness in temporary water can be removed by boiling, but hardness in permanent hard water cannot.

Give reason for the following:

Colloidal solutions exhibit brownian movement.

Give reason for the following:

The percentage of oxygen, in air dissolved in water, is higher than the percentage of oxygen in ordinary air.

Give reason for the following:

Washing soda can be used to remove both temporary and permanent hardness in water.

Match the substances in List I with the appropriate answer in List II.