Answer:
is a reactant; it is present before the reaction occurs.
Explanation:
In a chemical reaction the chemical formulas written before the arrow are described as reactants as they react together to form products which are written after the arrow.

Thus
and HCl are reactants here whereas
,
and
are products.
Answer:
Its b its the state not anything else
Heat capacity of aluminium = 0.900 J/g°C
While heat capacity of water = 4.186 J/g°C
Heat = heat gained by water + heat gained by aluminium
Heat gained by water = 100 × 4.186 × 30.5
= 12767.3 Joules
Heat gained by aluminium = 15 × 0.9 × 30.5
= 411.75 Joules
Heat required = 13179.05 Joules or 13.179 kJoules
Solution:- Hypochlorite ion
has one Cl and one O atom. Cl has 7 valence electrons and O has 6 valence electrons. Since there is one negative charge on the ion,
total valence electrons = 7 + 6 +1 = 14
(note:- if there is negative charge then it is added and if there is positive charge then it is subtracted while calculating the valence electrons)
Both Cl and O atoms wants to complete their octet and so for this we put a single bond between them. Single bond means two electrons, so the remaining electrons would be 14 - 2 = 12
It means 12 electrons will be placed as lone pair of electrons. To complete the octet, we put 6 dots around each of the atom. Oxygen is more electron negative than Cl, so we show the -1 charge for oxygen.
The chemical formula of oxalic is 
When oxalic acid reacts with water, first, oxalic acid removes one proton and results in the formation of mono acids.
After that, in second step, oxalic acid in aqueous solution removes another proton which shows it is a polyprotic acid.
The chemical equations are: (the reactions occurs in two steps due to presence to hydrogen atoms).
When one proton is removed:

When another proton is removed:

The dissociation of oxalic acid in water in shown in the image.