Do Acids increase the concentration of hydrogen ions in an aqueous solution?

Yes, they do

Explanation:

Since acids comprise of proton or hydrogen ions, when added to an aqueous solution. Proton or hydrogen concentration increases which lowers the pH

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.