Chemistry, asked by pcsys5494gmailcom, 6 months ago

c) 7 moldu
answer questions,
Give the scope of biochemistry
.
How does homogeneous mixture differ from heterogeneous mixture?
What is the relative atomic mass? How is it related to gram?
Define empirical formula with an example.
State three reasons why air is a mixture and water a compound?
Explain why hydrogen and oxygen are considered as elements whereas
water as a compound.
What is the significance of the symbol of an element?
State the reasons: soft drink is a mixture and water is a compound.
Classify the following into element, compound or mixture:
i. He and HD
ii. CO and Co iii. Water and milk
iv. Gold and brass 2. Iron and steel
Define atomic mass unit. Why is it needed?
(d) 1 mole of O. and I mole of CO.
Define industrial chemistry and analytical chemistry.
How can you differentiate between organic and inorganic chemistry?

Answers

Answered by kavitapahadiya058

Answer:

SuspensionSolvent(i) It has uniform compos ition.It does not have a uniform compos ition.(ii) No vis ible boundaries of s eparation.Shows vis ible boundaries of separation.(iii) They cons is t of only one phase.They cons is t of more than one phase.Example: sugar + water

→ sugar s olution.Example: s ugar + s and

NCERT TEXTBOOK PAGE 18

Q1. Differentiate between homogeneous and heterogeneous mixtures with examples.

Ans. Same as Q2 above.

Q2. How are sol, solution and suspension different from each other?

Ans.

Sol. (colloid)SolutionSuspension• Size of solute partic les between 1 nm to 100 nm.Siz e of solute partic les less than 1 nm (10-9m)Size of s olute partic les is more than 100 nm.• It is stable.Stable.Unstable.• It scatters a beam of light.It does not sc atter light.It s catters a beam of light.• Solute partic les pass through filter paper.Solute partic les passthrough filter paper.Solute particles do not pass through filter paper.

Q3. To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.

Ans. Mass of solute (sodium chloride) = 36 g

Mass of solvent (water) = 100 g

Mass of solution

= Mass of solute + Mass of solvent

= 36 g + 100 g = 136 g

NCERT TEXTBOOK PAGE 24

Q1. How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), which are miscible with each other?

Ans. A mixture of kerosene and petrol which are miscible with each other can be separated by distillation.

Method

• Take a mixture in a distillation flask.

• Fit it with a thermometer.

• Arrange the apparatus as shown in the figure.

• Heat the mixture slowly.

• Petrol vaporises first as it has lower boiling point.

It condenses in the condenser and is collected from the condenser outlet.

• Kerosene is left behind in the distillation flask.

Q2. Name the technique to separate

(i) butter from curd,

(ii) salt from sea-water,

(iii) camphor from salt.

Ans. (i) Centrifugation,

(ii) Evaporation,

(iii) Sublimation.

Q3. What type of mixtures are separated by the technique of crystallisation?

Ans. Crystallisation technique is used to purify solid with some impurities in it.

Example: Salt from sea-water.

NCERT TEXTBOOK PAGE 24

Q1. Classify the following as chemical or physical changes:

• cutting of trees,

• melting of butter in a pan,

• rusting of almirah,

• boiling of water to form steam,

• passing of electric current, through water and the water breaking down into hydrogen and oxygen gas,

• dissolving common salt in water,

• making a fruit salad with raw fruits and

• burning of paper and wood.

Ans.

Physical ChangeChemical Change• cutting of trees

• melting of butter in a pan

• boiling of water to form steam

• dissolving common salt in water

• making a fruit salad with raw fruits• rusting of almirah

• passing of electric current through water and then breaking down into hydrogen and oxygen gas

• burning of paper and wood

Q2. Try segregating the things around you as pure substances or mixtures.

Ans. Pure substances — Water, bread, sugar and gold.

Mixtures — Steel, plastic, paper, talc, milk and air.

QUESTIONS FROM NCERT

TEXTBOOK

Q1. Which separation techniques will you apply for the separation of the following?

(a) Sodium chloride from its solution in water.

(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.

(d) Different pigments from an extract of flower petals.

(e) Butter from curd.

(f) Oil from water.

(g) Tea leaves from tea.

(h) Iron pins from sand.

(i) Wheat grains from husk.

(j) Fine mud particles suspended in water.

Ans. (a) Evaporation (b) Sublimation

(e) Centrifugation (f) Separating funnel

(g) Filtration

(h) Magnetic separation

(i) Winnowing/sedimentation

(j) Decantation and filtration

Q2. Write the steps you would use for making tea. Use the words, solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.

Ans. 1. Take a cup of water in a container as solvent and heat it.

2. Add sugar in it which is solute. Heat it till all sugar dissolves.

3. You get a solution of water and sugar.

4. Sugar is soluble in water completely.

5. Add half a tea-spoon of tea-leaves, it is insoluble in water.

6. Boil the content, add milk which is also soluble in water, boil again.

7. Filter the tea with the help of strainer, the tea collected, in cup is filtrate and the tea leaves collected on the strainer is residue.

Q3. Pragya tested the solubility of three different substances at different temperatures and collected the data as given below

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