SLIP TEST-1 with Answers

                    ACIDS BASES AND SALTS

                                            SLIP TEST -1                 MARKS:25

I. ANSWER THE FOLLOWING QUESTIONS                  5 X 1 = 5 M

1. Write the characteristics of acids & bases ?

A. Acids are sour to taste . they turn blue litmus to red.

Bases are bitter to taste and soapy to touch. They turn red litmus to blue litmus.

2. How many types of indicators are there? what are they?

A.There are two types of indicators. They are Natural and synthetic indicators.

3. What is dilution?

A. Mixing an acid or base with water result in decrease in the concentration of ions (H3O+/OH–) per unit volume. This process is called dilution and the acid or the base is said to be diluted.

4. What is brine solution?

A.Brine solution is the aqueous solution of sodium chloride (NaCl).

5. Who introduced pH scale? pH scale Ranges from?

A. Sorensen introduced pH scale. It ranges from 0-14.

II. ANSWER THE FOLLOWING QUESTIONS                4 X 2 = 8 M

6. What is neutralization? Give two examples?

A.The reaction of an acid with a base to give a salt and water is known as a   neutralization reaction.

Acid + Base   - > Salt + Water

or

Base + Acid  - > Salt + Water

Ex: HCl + NaOH  - > NaCl + H2O

Ca (OH)2 + H2SO4  - >  CaSO4 + 2H2O

7. Write four uses of washing soda?

A. Uses of Washing soda:

1. Washing soda or sodium carbonate is used in glass, soap and paper industries.

2. It is used in the manufacture of sodium compounds such as borax.

3. Washing soda or sodium carbonate can be used as a cleaning agent for domestic

purposes.

4. It is used for removing permanent hardness of water.

5. Sodium carbonate is useful chemicals for many industrial processes.

8. Write four uses of bleaching powder?

A. Uses of Bleaching Powder:

1. Bleaching Powder is used for bleaching cotton and linen in the textile industry.

2. It is also used for bleaching wood pulp in paper industry.

3. It is used for bleaching washed clothes in laundry.

4. Used as an oxidizing agent in many chemical industries.

5. Used for disinfecting drinking water to make it free of germs.

6. Used as a reagent in the preparation of chloroform.

9. Why does tooth decay start when the pH of mouth is lower than 5.5?

1. Tooth decay starts when the pH of the mouth is lower than 5.5.

2. Tooth enamel, made of calcium phosphate is the hardest substance in the body.

3. It does not dissolve in water, but is corroded when the pH in the mouth is

below 5.5.

4. Bacteria present in the mouth produce acids by degradation of sugar and

food particles remaining in the mouth.

5. The best way to prevent this is to clean the mouth after eating food.

6. Using tooth pastes, which are generally basic neutralize the excess acid and

prevent tooth decay.

III. ANSWER THE FOLLOWING QUESTIONS               3 X 4 = 12 M

10. Compounds such as glucose and alcohols contain hydrogen but are not categorised as acids. Describe an activity to prove it?

A. Aim: To show acid solution in water conducts electricity or to observe the conductivity of alcohol, glucose and hydrochloric acid or Investigate whether all compounds containing hydrogen are acids or not.

Materials required: Beaker, graphite rods, bulb, connecting wire and 230V AC supply.

Procedure:

1) Prepare solutions of glucose, alcohol, hydrochloric acid and sulphuric acid.

2) Arrange graphite rods as electrodes in a beaker as shown in the figure.

3) Connect these rods to bulb and 230V AC supply with different coloured wires.

4) Pour some dil HCl in the beaker and switch on the connector.

5) We will notice that the bulb glows in this dil HCl solution.

6) Repeat this experiment by replacing dil HCl with alcohol and glucose and then we observe the bulb doesn’t glows.

7) Although alcohol and glucose solutions contain hydrogen their solutions doesn’t

have hydrogen ions.

8) So, current doesn’t flow through alcohol and glucose solutions.

9) In HCl solution H+ ions are present and these are responsible for conductivity and acidic property for HCl.

10) Alcohols and glucose doesn’t have H+ ions so they don’t treat as acids.

11. What is meant by "water of crystallization" ? Explain with an activity?

A. Aim: To remove water of crystallization or To find, are the crystals really dry?

Materials required: Dry test tube, test tube holder, Boiling tube burner and copper

sulphate crystals.

Procedure:

                                    

1) Take some crystals of copper sulphate (blue colour) in a dry test tube and heat

the test tube with burner.

2) The blue coloured copper sulphate changes its colour into white.

3) We observe water droplets on sides of the test tube.

4) This shows that the crystals of salts are not really dry.

5) Now add 2-3 drops of water on the sample of copper sulphate obtained after heating.

6) When the crystals are moistened with water, the blue colour reappears.

12. Write an experiment showing the reaction of acids with metals?

A.Aim: To show acids react with metals and liberate hydrogen gas.

Materials required: Test tube, delivery tube, glass trough, candle, soap water, dil HCl, and Zinc granules.

Procedure:

1. Arrange the apparatus as shown in the figure.

2. Take 10ml of dilute HCl in a test tube and add a few zinc granules to it.

3. Gas bubbles formed on the surface of the zinc granules.

4. Pass the gas being evolved through the soap water.

5. Gas filled bubbles rise into air through soap water.

6. Bring a burning candle near the gas filled bubble.

Observations:

1. Burning candle put off with pop sound and the evolved gas burns with blue flame. So,  the evolved gas is Hydrogen (H2).

2. Acids react with metals and give or liberate or evolve Hydrogen (H2) gas.

Chemical reaction of the above activity:

2 HCl (aq) + Zn(s)  - > ZnCl2 (aq) + H2 (g)

Repeat the above experiment with some other acids like H2SO4 and HNO3.

Generalization equation:

Acid + Metal  - > Salt + Hydrogen

Precautions:

1. Care should be taken while doing the experiments with acids.

2. Hydrogen gas is combustible. So, care should be taken while testing the evolved

gas with burning candle.

                                       ALL THE BEST