Answer:
A - 3
B - 6
Explanation:
The valency of hydrogen atom is +1
The valancy of an atom of other element combining with the hydrogen atom can be determined from the number of associated hydrogen.
when H combines with A, three atoms of hydrogen are used. Thus the valency of element A is -3
Now B combines with two molecules of A whose valency is -3
The valency of B would be twice the valency of element A i.e 6
if hydrogen combines with B, then the compound formed will be BH6
This technique can be used to make pure crystals of a soluble salt.
The burette is filled with hydrochloric acid.
A known quantity of alkali (say 50 cm3 sodium hydroxide)
is released from a pipette into the conical flask.
The tap on the burette is turned open to allow
the acid to be added drop by drop into the alkali.
The alkali contains an indicator (phenolphthalein)
which is pink in an alkali and colorless in an <span>acid.
</span>
When enough acid has been added to neutralize
the alkali, the indicator changes from
pink to colorless. This is the end point of the titration.
The titration<span> can be repeated using the </span><span>same amounts
</span><span>of </span>acid<span> and </span>alkali<span> but </span>without<span> the </span>indicator.
<span>Pure salt</span> crystals<span> which are </span>free<span> from </span><span>indicator
</span><span>can then be crystallized </span><span> from the </span>neutral<span> solution.</span>
It is called <span>absolute humidity.
</span>
Answer:
Mg -atomic number 12
electronic configuration -1s² 2s² 2p^6 3s²
