chapter 7

Question 1

why are a few anti-bumping granules added in the sea water before heating it

Answer 1

the granules can prevent bumping of sea water during distillation

Question 2

why is cold water passed into the condenser from the lower opening and leaves from the upper opening

Answer 2

to provide a better cooling effect for the water vapour

Question 3

how to do the flame test for the presence of sodium and chloride in common salt

Answer 3

dip a platinum wire or nichrome wire into a small amount of concentrated hydrochloric acidd

put the platinum wire in a blue Bunsen flame and observe the flame colour, no specific flame colour should be observed other than blue

moisten the clean platinum wire with concentrated hydrochloric acid and dip the wire into a crushed sample of the salt to be tested. let the small amount of salt be adhered to the surface of the platinum wire

heat the end of the wire strongly in the blue Bunsen flame and record its flame colour

Question 4

flame test result of sodium chloride

Answer 4

golden yellow

Question 5

flame test result of sodium carbonate

Answer 5

golden yellow

Question 6

flame test result of potassium chloride

Answer 6

lilac

Question 7

flame test result of potassium carbonate

Answer 7

lilac

Question 8

flame test result of calcium chloride

Answer 8

brick-red

Question 9

flame test result of calcium carbonate

Answer 9

brick-red

Question 10

flame test result of copper(II) chloride

Answer 10

bluish green

Question 11

flame test result of copper(II) carbonate

Answer 11

bluish green

Question 12

how to do the test for chloride ions in common salt (silver nitrate test)

Answer 12

put a small amount of magnesium chloride into a test tube

add 5cm3 of distilled water to the test tube to dissolve the sample salt

add about 10 drops of dilute silver nitrate solution followed by 2cm3 (excess amount) of dilute nitrate acid

if white precipitates appear, it indicates the presence of chloride ions in the sample solution

Question 13

word equation of the reaction of silver nitrate test

Answer 13

metal chloride + silver nitrate –> silver chloride + metal nitrate

Question 14

test for water

Answer 14

using anhydrous copper (II) sulphate
the solid changes from white to blue

using dry cobalt(II) chloride paper
the paper turns from blue to pink

Question 15

what is brine

Answer 15

sea water or concentrated sodium chloride solution

Question 16

use of hydrogen from electrolysis of brine

Answer 16

make margarine, ammonia, fertilizers

Question 17

use of chlorine from electrolysis of brine

Answer 17

to make PVC (polyvinyl chloride which is a plastic)

Question 18

use of sodium hydroxide solution

Answer 18

used in paper industry, treatment of acidic or heavy metal effluents from factories

Question 19

what does marble contain

Answer 19

calcium carbonate

Question 20

limestone

Answer 20

hard and strong

used in building industry such as making cement

Question 21

chalk

Answer 21

slightly softer

used in building industry

Question 22

marble

Answer 22

crystalline solid

very hard

used for building statues, monuments, and as floors and walls in some buildings

Question 23

what is calcium oxide known as

Answer 23

quicklime

Question 24

what is calcium hydroxide known as

Answer 24

slaked lime

Question 25

thermal decomposition of calcium carbonate

Answer 25

calcium carbonate -----heat----> calcium oxide + carbon dioxide calcium oxide + water ----> calcium hydroxide

Question 26

how to do the test for metal carbonate

Answer 26

pour some limewater into a test tube until it is one quarter full insert a delivery tube into the limewater put 3 spatula (1.5grams) of calcium carbonate into a boiling tube measure 10cm3 of dilute hydrochloric acid. add it to the boiling tube and immediately stopper the boiling tube with the cork joined to the delivery tube tube shake the boiling tube slightly to mix the contents. observe what happens to the reaction mixture and the limewater

Question 27

what can you observe in the boiling tube containing calcium carbonate and dilute hydrochloric acid

Answer 27

effervescence occurs and the boiling tube becomes warm

Question 28

what happens to the limewater

Answer 28

it turns milky

Question 29

word equation between calcium carbonate and dilute hydrochloric acid

Answer 29

calcium carbonate + dilute hydrochloric acid -----> calcium chloride + carbon dioxide + water

Question 30

why has the reaction mixture turned milky

Answer 30

the carbon dioxide given out has reacted with calcium hydroxide in limewater to give insoluble calcium carbonate which is white in colour, so the reaction has turned milky

Question 31

word equation for the mixture reaction to turn milky

Answer 31

calcium hydroxide solution + carbon dioxide ----> calcium + carbonate + water

Question 32

what is calcium hydroxide solution

Answer 32

limewater