Density is mass over volume. If you put it into a formula it would look like this:

Based on the problem given, you can see that the mass of the aluminum block is 82.0 g and the volume is 12.8 cm3. Just put that into your equation and solve for it:
The answer is then letter C.
It would be 18 electrons i think
Answer:
(A). C6H5Br + Mg(in ether) -----------> C6H5MgBr.
(B). C6H5MgBr + O = C = O -----------> C6H5-COO^- Mg^+ Br.
(C). C6H5-COO^- Mg^+ Br + HCl --------> C6H5-COOH + Mg^+Br(OH).
PRODUCTS=> C6H5-COOH and Mg^+Br(OH).
Explanation:
A Grignard reagent is a reagent that/which is an organometallic compound that is R -Mg- X. The R = alkyl, vinyl or allyl and the X = halogens.
It must be noted that an important reaction of Grignard reagent is its reaction with compounds containing the Carbonyl that is -CO functional group and this kind of Reaction is known as a Grignard Reaction.
So, in this question we are told that;
=> "1-bromo-benzene andits subsequent reaction with solid carbon dioxide (CO2) followed by acidic workup (using HCl asthe acid). "
Thus;
(A). C6H5Br + Mg(in ether) -----------> C6H5MgBr.
(B). C6H5MgBr + O = C = O -----------> C6H5-COO^- Mg^+ Br.
(C). C6H5-COO^- Mg^+ Br + HCl --------> C6H5-COOH + Mg^+Br(OH).
In NH4OH, the compounds that make it up are NH4+ and OH-
Therefore N exists in the ammonium form.
In the ammonium ion 4H atoms are connected to N.
N is more electronegative than H, therefore when H bonds to N, H is the more positive atom therefore each H has a charge of +1, since there are 4 H atoms the charge contributed by the 4H atoms are +1 * 4 = +4
the overall charge of NH4 is +1
Charge of N (+) +4 = +1
Charge of N = +1 - 4
Therefore oxidation state of N in NH4 is = -3
4 because electrons and protons have the same magnitude and electron is - and proton is +.