When HCl reacts with a metal, hydrogen gas will be evolved. To test this gas, insert a burning splinter into the outlet of gas, the flame will be extinguished with a pop sound. This will confirm the gas is hydrogen.
The answer should be 3 moles of Carbon.
As you move from left to right on the periodic table, atomic size and electronegativity increase.
(Ionization energy increases from left to right on the periodic table, and electronegativity relates to ionization energy in that the higher the ionization energy, the higher the electronegativity.)
(Atomic radius increases from left to right on the periodic table due to the fact that electrons are gradually being added from left to right, meaning the amount of protons in the nucleus are increasing in order to keep the atom neutral, therefore atomic size/radius increases.)