Workbook Answers 7.1

A

1.     False

2.     True

3.     True

4.     True

5.     False

B

1.     B

2.     C

3.     B

4.     B

5.     C

6.     A

7.     B

C

1.     (a)    mixture

        (b)    nitrogen

        (c)    oxygen

        (d)   carbon dioxide

        (e)    water vapour

        (f)    noble gases

2.     relights

3.     (a)    red

        (b)    yellow

4.     (a)    colourless

        (b)    milky

5.     cobalt chloride paper

D

(a)    iii

(b)    v

(c)    i

(d)   iv

(e)    vi

(f)    ii

E

1.     (a)    A-nitrogen; B-oxygen; C-carbon dioxide

(b)    Sample Y is breathed air, because it contains more carbon dioxide (gas C) and less oxygen (gas B).

(c)    Test gas B with a glowing splint. The glowing splint relights, showing that gas B is oxygen. (or other reasonable answers)

2.     (a)    (i)     carbon dioxide

                (ii)    red

                (iii)   yellow

                (iv)   from colourless to milky

(b)    (i)     Incorrect. It is because both hydrogencarbonate indicator and lime water cannot be used to confirm the presence of other gases.

(ii)    She should test ‘gas X’ with a glowing splint, if the glowing splint relights, the gas is oxygen.

        (c)    (i)     In breathed air, the indicator changes from red to yellow.

                        In unbreathed air, the indicator remains unchanged.

                (ii)    Breathed air contains more carbon dioxide than unbreathed air.