Question:
Why air is a mixture not a compound? Give reasons.
Answer:
Air is a mixture for of the following reasons:
- Air does not have a fixed composition. Its composition varies from place to place.
- The components of air can be separated by a physical method such as fractional distillation of liquid air.
- Liquid air does not have a definite boiling point.
- We can prepare air artificially by mixing the various components of air in the same proportions in which they occur at a place. This is a physical process because no energy changes occur.
Is Matter Around Us Pure?
Q 1.
Identify the following as mixture or compound.
(i) blood
(ii) common salt
(iii) sugar
(iv) brass
Q 2.
State the differences between compounds and mixtures.
Q 3.
What is a solution? What are the properties of a solution?
Q 4.
What are the characteristics exhibited by a pure substance?
Q 5.
What are the properties of suspensions?
Q 6.
What are the differences and similarities between concentration and solubility?
Q 7.
Name two properties of a substance to check its purity?
Q 8.
What are the reasons for separating the constituents of a mixture?
Q 9.
What are the physical states of dispersed phase and dispersion medium of a fog?
Q 10.
What factors affect the solubility of solvent and solute?
Q 11.
What are suspensions? Explain with an example.
Q 12.
What is meant by a pure substance?
Q 13.
To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293K. Find its concentration at this temperature.
Q 14.
How crystallization is better than evaporation?
Q 15.
Why air is a mixture not a compound? Give reasons.
Q 16.
What are the advantages of preparing solutions?
Q 17.
Name the elements are in liquid state at room temperature.
Q 18.
Based on the type of solvent, how solutions are classified?
Q 20.
Based on the amount of solute in the given solution, how solutions are classified?
Q 21.
What are the properties of a colloid?
Q 22.
How many elements are there which are in gaseous state at room temperature?
Q 23.
List the points of differences between homogeneous and heterogeneous mixtures.
Q 24.
A good method to separate alum (phitkari) from impure samples is
(a) Filtration
(b) Sedimentaion
(c) Crystallization
(d) Sublimation
Q 25.
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Q 26.
What are the physical states of dispersed phase and dispersion medium of a cloud?
Q 27.
State three reasons why you think air is a mixture and water is a compound.
Q 28.
How will you separate iron pins from sand ?
Q 29.
Name the technique to separate
(i) butter from curd
(ii) salt from sea-water
(iii) camphor from salt
Q 30.
Name the process you would use to separate a mixture of two miscible liquids (like acetone and water).
Q 31.
What are the various methods to express concentration of a solution?
Q 32.
What is Chromatography?
Q 33.
Choose one term from the following which includes the other three :
aerosol,
emulsion,
colloid,
sol
Q 34.
What is difference between colloids and suspensions ?
Q 35.
Fill in the following blanks with suitable words :
(a) An element is made up of only one kind of...........atoms
(b)Brine is a..........whereas alcohol is a.......
(c) Brass is an alloy which is considered a..........
(d) The three important metalloids are.............and...........
(e) The elements which are sonorous are called...............
Q 36.
21.5 g of sodium chloride dissolves in 60 g of water at 25°C. Calculate the solut water at that temperature.
Q 37.
(a) What is a physical change ? Give two examples of physical changes.
(b) What is a chemical change ? Give two examples of chemical changes.
Q 38.
(a) What is meant by a solution ? Give two examples of solutions.
(b)What is a suspension ? Give two examples of suspensions.
(c)
Q 39.
Name the process you would use to separate a mixture of water and alcohol.
Q 40.
What is meant by Solubility?
Q 41.
Calculate the mass of glucouse and mass of water required to make 200g of 25% solution of glucouse.
Q 42.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 43.
Which technique can be used to detect and identify traces of poison present in the stomach wash of a person ?
Q 44.
How would you separate a mixture of sugar and salt ?
Q 45.
Classify the following into elements and compounds :
(i)
Q 46.
Is air a mixture or a compound ? Give three reasons for your answer.
Q 47.
Which of the following is a sol ?
Shaving cream,
Milk,
Fog,
Soap solution,
Hairspray
Q 48.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 49.
Name one pair of substances whose mixture can be separated completely by distillation.
Q 50.
(a) Name the process by which common salt is obtained from sea-water.
(b) Name the process by which common salt is purified.
