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Question is incomplete. Complete question is attached below
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Answer: Option A: HCO3-(aq.)
Reason:
From the reaction, it can be seen that following reaction occurs in forward direct
HCO3-(aq) + H2O(l) → H2CO3(aq) + OH-(aq)
In above forward reaction, HCO3- accepts proton from H2O to generate H2CO3. Thus, according to Lowry and Bronsted theory of acid-base,
HCO3- is a base, while
H2CO3 is a conjugate acid.
Answer: 4000000000
because 20X200000000=4000000000
Answer : The Lewis-dot structure of
is shown below.
Explanation :
Lewis-dot structure : It shows the bonding between the atoms of a molecule and it also shows the unpaired electrons present in the molecule.
In the Lewis-dot structure the valance electrons are shown by 'dot'.
The given molecule is, 
As we know that rubidium has '1' valence electrons, iodine has '7' valence electrons and oxygen has '6' valence electrons.
Therefore, the total number of valence electrons in
= 1 + 7 + 2(6) = 20
As we know that
is an ionic compound because it is formed by the transfer of electron takes place from metal to non-metal element.
B is the answer , i got you