c5g

potential Hydrogen

Strong acids lose all their hydrogen ions - so they dont attract them - low pH

Weak acids regain ions - pH higher

Alkalis attract Hydrogen ions - combine with hydrooxide ions to make water - pH very high

Alkalis contain OH-  and attract H+ because they always want to make H2O

Calcium carbonate + hydrochloric acid - fast reaction

calcium carbonate + ethanoic acid - slow reaction because it is a weaker acid and few ions so fewer collisions

If the same amount of acid and calcium carbonate is used in each case the volume of carbon dioxide produced will be the same.  It will just happen at a slower rate when the weaker acid is used. 

amount means moles not volume or mass