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9th Class Examination 2015 Chemistry important Question / Notes Chapter 6 to 8

9th Class Examination 2015 Chemistry  important Question / Notes  Chapter 6 to 8

1. Define solvent and solute.
2. Why we stir paints thoroughly before using?
3. What do you mean by volume/volume %?
4. Define solubility.
5. Why test-tube becomes cold, when KNO3 is dissolved in water?
6. What is difference between colloid and suspension?
7. What is Tyndall effect and on what factors it depends?
8. What is supersaturated solution?
9. What are dilute and concentrated solutions?
10. Define molarity. Give its formula and unit.

Long Questions 5×1=5
(a) What is meant by concentration of a solution? Describe the different ways of expressing the percentage composition of solution. 3
(b) When we dissolve 20g of NaCl in 400cm3 of a solution, what will be its molarity? 2
1. Differentiate between oxidizing and reducing agents.
2. Why O2 is necessary for rusting?
3. Differentiate between strong and weak electrolyte.
4. Why galvanizing is done?
5. Define corrosion.
6. Where does the sodium metal is collected in Downs cell?
7. Which type of chemical reaction takes place in electrolytic cell?
8. What is the difference between valency and oxidation state?
9. Name the by-products produced in Nelson’s cell.
10. Define oxidation-reduction or redox reaction.

Long Questions 5×1=5
1. (a) What is electroplating? How electroplating of chromium is carried out? 3
(b) Write down the rules for assigning oxidation state or oxidation number. 2
1. Why the second ionization energy of magnesium is higher than the first one?
2. Why copper is used for making electrical wires?
3. Why ionization energy of Na is less than Mg?
4. Write down some properties of gold.
5. Why platinum is used for making jewelry?
6. Why is HF a weak acid?
7. What is difference between metals and non-metals?
8. How oxygen reacts with group II A metals?
9. What is relationship between electropositivity and ionization energy?
10. What do you mean by 24 carat gold?

Long Questions 5×1=5
1. (a) Write a note on the significance of non-metals. 2.5
(b) Compare and contrast the properties of alkali and alkaline earth metals. 2.5

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