GUESS QUESTIONS ACID BASES AND SALTS

GUESS QUESTIONS

ACID, BASES AND SALTS

INDICATORS

1.       You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?

2.       What is the colour of litmus in a solution of ammonium hydroxide.

3.       What would be the colour of litmus in a solution of sodium carbonate.

ACID (PHYSICAL PROPERTIES)

4.       While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

5.        How is the concentration of hydronium ions (H3O+) affected when a solution of an acid is diluted?

6.       Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?

7.       Why does an aqueous solution of an acid conduct electricity?

8.       Why does dry HCl gas not change the colour of the dry litmus paper?

9.       Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids. Describe an Activity to prove it.

10.   Why does distilled water not conduct electricity, whereas rain water does?

11.   Why do acids not show acidic behaviour in the absence of water?

ACID (CHEMICAL PROPERTIES)

12.   Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence ofthis gas?

13.   Write word equations and then balanced equations for the reaction taking place when –

(a) dilute sulphuric acid reacts with zinc granules.

(b) dilute hydrochloric acid reacts with magnesium ribbon.

(c) dilute sulphuric acid reacts with aluminium powder.

(d) dilute hydrochloric acid reacts with iron filings.

14.   Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH3COOH) is added to test tube B. In which test tube will the fizzing occur more vigorously and why?

15.   Why should curd and sour substances not be kept in brass and copper vessels?

16.   Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.

17.    A solution reacts with crushed egg-shells to give a gas that turns lime-water milky.The solution contains which acid

BASE (PHYSICAL PROPERTIES)

18.   What is an alkali.

19.   How is the concentration of hydroxide ions (OH–) affected when excess base is dissolved in a solution of sodium hydroxide?

20.   Do basic solutions also have H+(aq) ions? If yes, then why are these basic?

BASE  (CHEMCIAL PROPERTIES)

BASE (USES)

21.   Why antacid is considred as medicines for treating indigestion?

PH

22.   You have two solutions, A and B. The pH of solution A is 6 and pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic?

23.   What effect does the concentration of H+(aq) ions have on the nature  or pH of the solution?

24.   Under what soil condition do you think a farmer would treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)?

25.   Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

26.   Why does 1 M HCl solution have a higher concentration of H+ ions than 1 M CH3Cooh solution.

27.   A milkman adds a very small amount of baking soda to fresh milk.

(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?

(b) Why does this milk take a long time to set as curd?

APPLICATION OF PH IN DAILY LIFE

28.   Why does tooth decay start when the pH of mouth is lower then 5.5 ?

SALTS

29.   What is a neutralisation reaction? Give two examples.

30.   10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount HCl solution (the same solution as before) required to neutralise it will be (a) 4 mL (b) 8 mL (c) 12 mL (d) 16 mL

SOLVAY PROCESS

31.   Name the product formed  if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.

32.   Give two important uses of washing soda and baking soda.

33.   Name the sodium compound which is used for softening hard water.

HANSCLEVER’S PROCESS

34.   What is the common name of the compound CaOCl2

35.   Write the name and chemical formula of the calcium compound used for disinfecting drinking water. How is this compound manufactured.

36.   Name the substance which on treatment with chlorine yields bleaching powder.

PLASTER OF PARIS

37.   Write an equation to show the reaction between Plaster of Paris and water.

38.   Plaster of Paris should be stored in a moisture-proof container. Explain why?

WATER  OF CRYSTALLISATION

1.       What is meant by water of crystallization of a substance ? Describe an activity to show that blue copper sulphate crystals contain water of crystallization.

2.       Crystals of copper sulphate are heated in a test tube for some time.

a.       What is the colur of copper sulphate crystals before and after heating.

b.       What is the source of liquid droplets seen on the inner upper side of the test tube during the heating process.