10th Science Guide Unit 9 SOLUTIONS

10th Standard Science Physics Lesson 9 SOLUTIONS Book Back Answers | Samacheer Kalvi Guide

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10th Science Guide Unit 9 SOLUTIONS – Book Back Answers

 

Formulae
Solubility	mass of the solute/mass of the solvent x 100
Mass Percentage	mass of the solute/mass of the solvent x 100
Volume Percentage	volume of the solute/Volume of the solute + volume of sovent x 100

I. Choose the correct answer.

1. A solution is a __________ mixture.

1. homogeneous
2. heterogeneous
3. homogeneous and heterogeneous
4. non homogeneous

Ans ; homogeneous

2. The number of components in a binary solution is __________.

1. 2
2. 3
3. 4
4. 5

Ans ; 2

3. Which of the following is the universal solvent?

1. Acetone
2. Benzene
3. Water
4. Alcohol

Ans ; Water

4. A solution in which no more solute can be dissolved in a definite amount of solvent at a given temperature is called __________.

1. Saturated solution
2. Un saturated solution
3. Super saturated solution
4. Dilute solution

Ans ; Saturated solution

5. Identify the non aqueous solution.

1. sodium chloride in water
2. glucose in water
3. copper sulphate in water
4. sulphur in carbon–di–sulphide

Ans ; sulphur in carbon–di–sulphide

6. When pressure is increased at constant temperature the solubility of gases in liquid __________.

1. No change
2. increases
3. decreases
4. no reaction

Ans ; increases

7. Solubility of NaCl in 100 ml water is 36 g. If 25 g of salt is dissolved in 100 ml of water how much more salt is required for saturation __________.

1. 12g
2. 11g
3. 16g
4. 20g

Ans ; 11g (36–25)

8. A 25% alcohol solution means;

1. 25 ml alcohol in 100 ml of water
2. 25 ml alcohol in 25 ml of water
3. 25 ml alcohol in 75 ml of water
4. 75 ml alcohol in 25 ml of water

Ans ; 25 ml alcohol in 75 ml of water

9. Deliquescence is due to __________.

1. Strong affinity to water
2. Less affinity to water
3. Strong hatred to water
4. Inertness to water

Ans ; Strong affinity to water

10. Which of the following is hygroscopic in nature?

1. ferric chloride
2. copper sulphate penta hydrate
3. silica gel
4. none of the above

Ans ; silica gel

II. Fill in the blanks

1. The component present in lesser amount, in a solution is called __________. Ans ; solute
2. Example for liquid in solid type solution is __________. Ans ; Mercury with sodium
3. Solubility is the amount of solute dissolved in __________ g of solvent. Ans ; 100
4. Polar compounds are soluble in __________ solvents. Ans ; polar
5. Volume persentage decreases with increases in temperature because __________. ns ; expansion of liquid

III. Match the following

• Blue vitriol           – CaSO₄.2H₂O
• Gypsum – CaO
• Deliquescence     – CuSO₄.5H₂O
• Hygroscopic         – NaOH

Ans ; 1- c, 2 – a, 3 – d, 4 – b

IV. True or false (If false give the correct statement)

1. Solutions which contain three components are called binary solution. ( False )

• Solutions which contains two components are called binary solution.

2. In a solution the component which is present in lesser amount is called solvent. ( False )

• In a solution, the component which is present in higher amount is called solvent.

3. Sodium chloride dissolved in water forms a non-aqueous solution. ( False )

• Sodium chloride dissolved in water forms a aqueous solution. ( False )

4. The molecular formula of green vitriol is MgSO₄.7H₂O.

• The molecular formula of epsom salt is MgSO₄.7H₂O.

5. When Silica gel is kept open, it absorbs moisture from the air, because it is hygroscopic in nature. ( True )

V. Short answer questions

1. Define the term: Solution.

Solution is a homogeneous mixture of two or more substances.

2. What is mean by binary solution.

A solution contains two components is called Binary solution. Eg. Salt in water, Sugar in water.

3. Give an example each.

1. i) gas in liquid.

• Soda water.

1. ii) solid in liquid.

• Sodium chloride in water.

iii) solid in solid.

• Copper dissolved in Gold (alloys).

1. iv) gas in gas.

• Mixture of He – O2 gases.

4. What is aqueous and non-aqueous solution? Give an example.

1. i) Aqueous solution :

• The solution in which water acts as a solvent is called aqueous solution. eg: Common salt in water, sugar in water.

1. ii) Non–aqueous solution :

• The solution in which any liquid other than water, acts as a solvent is called non–aqueous solution. eg: Sulphur dissolved in carbon di sulphide, iodine dissolved in ccl4.

5. Define Volume percentage.

Volume percentage is defined as the percentage by volume of solute present in the given volume of the solution.

Volume percentage = Volume of the solute/Volume of the solute + Volume of the solvent × 100

Volume percentage = Volume of the solute/Volume of the solution x 100

6. The aquatic animals live more in cold region. Why?

Because, more amount of dissolved oxygen is present in the water of cold regions. This shows that the solubility of oxygen in water is more at low temperature.

7. Define Hydrated salt.

The number of water molecules found in the crystalline substance is called water of crystallisation. Such salts are called hydrated salts.

8. A hot saturated solution of copper sulphate forms crystals as it cools. Why?

The number of water molecules in blue vitriol is five, so its water of crystallisation is 5. When blue coloured

copper sulphate crystals are gently heated, it loses its 5 water molecules and becomes anhydrous copper sulphate. Then add a few drops of water or allow it to cool, the colourless anhydrous salt again turns back into blue coloured hydrated salt.

9. Classify the following substances into deliquescent, hygroscopic.

Conc. Sulphuric acid, Copper sulphate penta hydrate, Silica gel, Calcium chloride, and Gypsum salt.

Deliquescent	Hygroscopic
Calcium Chloride	i) conc. H2SO4 ii) Silica gel iii) Copper sulphate penta hydrate iv) Gypsum salt

 

10th Science Guide Unit 9 SOLUTIONS

VI. Long answer questions

1.Write notes on;

1. i) Saturated solution.
2. ii) Unsaturated solution

Saturated Solution	Unsaturated Solution
A solution in which no more solute can be dissolved in a definite amount of the solvent at a given temperature is called saturated solution.	A solution is one that contains less solute than that of the saturated solution at a given temperature.
eg: 36 g of sodium chloride in 100 g of water at 25° C.	eg: 10 g (or) 20 g (or) 30 g of sodium chloride in 100 g of water at 25° C form unsaturated solution.

2. Write notes on various factors affecting solubility.

Factors affecting solubility : There are three main factors which govern the solubility of solute. They are;

• i) Nature of the solute and solvent.
• ii) Temperature.
• iii) Pressure.

Nature of the solute and solvent :

The nature of the solute and solvent plays an important role in solubility. Although water dissoves an enormous variety of substances, both ionic and covalent, it does not dissove everything.

For example: Common salt is a polar compound and dissolves in polar solvent like water.

Non–polar compounds aresoluble in non–polar solvents.

For example: Fat dissolved in Ether.

Effect of temperature :

Solubility of a soled solute in a liquid solvent increases with increase in temperature.

In endothermic Process :

Solubility increases with increase in temperature.

In exothermic Process :

Solubility decreases with increase in temperature.

Solubility of gases in liquid :

Solubility of gases in liquid decrease with increase in temperature. Generally water contains dissolved oxygen. When water is boiled the solubility of oxygen in water decreases. So oxygen escapes in the form of bubbles.

Effect of pressure :

When the pressure is increased, the solubility of a gas in liquid increases. Eg.: Carbonated beverages.

3. a) What happens when MgSO4.7H2O is heated? Write the appropriate equation.

Its water of crystallisation is 7. When magnesium sulphate hepta hydrate crystals are genetly heated, it loses seven water molecules and becomes an hydrous magnesium sulphate.

gSO4.7H2O   (Magnesium sulphate heptahydrate)

Heating   Cooling

MgSO4 + 7H2O Anhydrous Magnesium  sulphate)

b) Define solubility.

Solubility is defined as the number of grams of solute that can be dissolved in 100 g of a solvent to form its saturated solution at a given temperature and pressure. For example 36 g of sodium chloride need to be dissolved in 100 g of water to form its saturated solution at 25° C. Thus the solubility of NaCl in water is 36 g at 25° C. The solubility is mathematically expressed as,

Solubility = Mass of the solute/Mass of the solvent× 100

4. In what way hygroscopic substances differ from deliquescent substances.

Hygroscopic	Deliquescent
When exposed to the atmosphere at ordinary temperature, they absorb moisture and do not dissolve.	When exposed to the atmospheric air at ordinary temperature, they absorb moisture and dissolve.
Hygroscopic substances do not change its physical state on exposure to air.	Deliquescent substances change its physical state on exposure to air.
Hygroscopic substances may be amorphous solids or liquids.	Deliquescent substances are crystalline solids.

5. A solution is prepared by dissolving 45 g of sugar in 180 g of water. Calculate the mass percentage of solute.

Given :    Mass of the solute = 45 g, Mass of the solvent = 180g

Mass Percentage	= Mass of the solute/Mass of the solute + Mass of the solvent x 100
	= 45g/45g + 180g x 100
	= 45/225 x 100 = 20%.

6. 3.5 litres of ethanol is present in 15 litres of aqueous solution of ethanol. Calculate volume percent of ethanol solution.

Given :

Volume of the solute = 3.5 lit of ethanol, Volume of the solution = 15 lit.

Volume Percentage	= Volume of the solute/Volume of the solution x 100
	= 3.5 lit/15 lit ×100
	= 0.7/3 × 100 = 70/3
Volume Percentage	= 23.33%.

VIII. HOT question

1. Vinu dissolves 50 g of sugar in 250 ml of hot water, Sarath dissolves 50 g of same sugar in 250 ml of cold water. Who will get faster dissolution of sugar? and Why?

50 g of sugar in 250 ml of hot water. Because heat is expanse the molecules of water. So it is easily dissolved.

2. ‘A’ is a blue coloured crystaline salt. On heating it loses blue colour and to give ‘B’. When water is added, ‘B’ gives back to ‘A’. Identify A and B, write the equation.

A is a blue coloured crystalline salt => Copper Sulphate Penta hydrate

CuSO₄.5H₂O (blue vitriol)

The equation is,

CuSO4.5H2O   Copper sulphate penta hydrate (blue colour)

Heating Cooling

CuSO4 + 5H2O   Anhydrous copper sulphate (colourless

3. Will the cool drinks give more fizz at top of the hills or at the foot? Explain.

Cool drinks give more fizz at top of hills because solubility of gas is low at altitude and hence the carbon dioxide less soluble in cool drinks at altitude gives more fizz.