chemistry

it's because copper is not reactive enough to react with dilute hydrochloric acid
that is, copper tend to become metal but not ion in dilute hydrochloric acid
in e.c.s. table
metal below copper is less reactive than copper
so they cannot react with dilute hydrochloric acid also

2007-05-18 22:01:12 補充：
from the table of the first answereras you can seecopper and other metals below it are all below hydrogen

2007-05-18 22:01:21 補充：
this means that copper and the metals below it are less reactive than hydrogensince they are less reactive than hydrogenthey cannot displace hydrogen from dilute hydrochloric acidso they have no reaction with dilute hydrochloric acid

because they have a higher tendercy to lose electrons
HKCEE 係要求咁答既.

Compared with Cu(d-block element),

∵metals above copper in the E.C.S. table shown above
have smaller in size and relatively lower secreening effect，
it forms ions easily and reacts the hydrogen ions in the duilte hydrochloric acid
∴ it will form a more stable form.

圖片參考：http://www.wpbschoolhouse.btinternet.co.uk/page03/3_33reactivity/reactivityfinal1.gif


圖片參考：http://www.wpbschoolhouse.btinternet.co.uk/page12/gifs/ReactivitySeriesList.gif


As you may see in the above reactivity series, the lower the element is in the series, the less reactive it is. So, hydrogen is placed there for comparison. Only the metals above hydrogen can react with diluted hydrochloric acid.

Maybe you may say it this way, copper is too unreactive to react with diluted hydrochloric acid.