To know this, you will need to know the solubility rules, which
are:
- Salts containing Group I elements (Li+, Na+, K+, Cs+, Rb+) are
soluble . There are few exceptions to this rule. Salts containing
the ammonium ion (NH4+) are also soluble.
- Salts containing nitrate ion (NO3-) are generally soluble.
- Salts containing Cl -, Br -, or I - are generally soluble.
Important exceptions to this rule are halide salts of Ag+, Pb2+,
and (Hg2)2+. Thus, AgCl, PbBr2, and Hg2Cl2 are insoluble.
- Most silver salts are insoluble. AgNO3 and Ag(C2H3O2) are
common soluble salts of silver; virtually all others are
insoluble.
- Most sulfate salts are soluble. Important exceptions to this
rule include CaSO4, BaSO4, PbSO4, Ag2SO4 and SrSO4 .
- Most hydroxide salts are only slightly soluble. Hydroxide salts
of Group I elements are soluble. Hydroxide salts of Group II
elements (Ca, Sr, and Ba) are slightly soluble. Hydroxide salts of
transition metals and Al3+ are insoluble. Thus, Fe(OH)3, Al(OH)3,
Co(OH)2 are not soluble.
- Most sulfides of transition metals are highly insoluble,
including CdS, FeS, ZnS, and Ag2S. Arsenic, antimony, bismuth, and
lead sulfides are also insoluble.
- Carbonates are frequently insoluble. Group II carbonates
(CaCO3, SrCO3, and BaCO3) are insoluble, as are FeCO3 and
PbCO3.
- Chromates are frequently insoluble. Examples include PbCrO4 and
BaCrO4.
- Phosphates such as Ca3(PO4)2 and Ag3PO4 are frequently
insoluble.
- Fluorides such as BaF2, MgF2, and PbF2 are frequently
insoluble.
Basing on these rules, the reactions are as follow:
1. K2SO4 + CuCl2 -------->
CuSO4 + 2KCl
2. K2SO4 + CaCl2 -------->
CaSO4 + 2KCl
3. K2SO4 + MgCl2 -------->
MgSO4 + 2KCl
4. K2SO4 + FeCl2 -------->
FeSO4 + 2KCl
Now with the rules, you will know the state of these
compounds.
Hope this helps