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1. Experiment to prove that oxygen is used up
in respiration (Fig. 7.2).
An apparatus is arranged as shown in Fig. 7.2.
Flask (A) contains germinating bean seeds and flask
(B) has dead (boiled) seeds together with some
antiseptic (such as carbolic acid) to avoid bacterial
decay. Wet cotton provides water to both samples.
A small tube containing soda lime (a mixture of
sodium hydroxide and calcium oxide) is suspended
in each flask for absorbing any carbon dioxide
released by the seeds. After a few days, the delivery
tube connected with flask (A) will show a greater
rise in water level. When a burning paper is
introduced into each flask after removing their
corks, the flame is immediately put off in flask (A),
but it continues for a short while in flask (B). This
proves that oxygen was absent in flask (A) thereby
showing that it was used up by the germinating
seeds and the volume of oxygen so used up was
indicated by the rise of water level in the delivery
tube. There are two simple questions which you can
surely answer. Why is there a slight increase in the
level of water in the delivery tube of flask (B)?
Which of the two flasks, (A) or (B), is a control?
FLASKA
FLASK B
what is the Method,
Things required ,
Description ,
Conclusion .
plz answer
Answers
Explanation:
Requirements:
A conical flask, a bent tube, germinating seeds, caustic potash in a small container, a mercury dish.
Method:
Germinating seeds are taken in a conical flask in which a container of caustic potash is also put. The mouth of this conical flask is closed by a single-holed cork through which a glass tube bent twice at right angles in inserted. The far end of this tube is put in the mercury dish. Now this apparatus is left undisturbed for some time.
Observation:
The mercury in far end of bent glass tube rises to a height of 15 cm.
Explanation:
The germinating seeds undergo aerobic respiration as they use the oxygen available inside the conical flask. As whole of the oxygen is used up by the germinating seeds, the pressure inside the flask is decreased. Hence, consequently the mercury level rises in the far end of the bent glass tube.
This level reaches only a height of 15 cm in the glass tube. As this level is about one-fifth the air. As oxygen constitutes one fifth of total composition, it is reasonable to infer that the seeds have used this gas of the air in respiration.
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