what are the chemical formulas for calcium phosphate, calcium carbonate, and potassium phosphate?
Look at the periodic table. Ca is in group IIA (or group 2 depending upon the system you are using) so it has a valence of +2. Phosphate is one of those polayatomic ions you must memorize. It is -3. Carbonate is -2. K is in group IA or group 1. Now you hve the info you need to determine the formulas.
Calcium phosphate comes up with the same formula as calcium carbonate...is that correct?
No. Calcium carbonate is correct at CaCO3. Ca is +2 and carbonate is -2; therefore, CaCO3 is the empirical formula. PO4^-3 is the phosphate ion. Put Ca and PO4 together, with Ca +2 and PO4 a -3.
so, Ca3(PO4)2?
and is monocalcium phosphate the same thing as calcium phosphate?
right on calcium phosphate.
No on monocalcium phosphate. It CAN'T be the same thing because you just wrote Ca3(PO4)2 which would be tricalcium phosphate, would it not? As Bob Pursley suggested in an earlier response, monocalcium phosphate is another name for monocalcium dihydrogen phosphate. Your teacher probably wants you to figure out that if you have monocalcium, then there must be two hydrogens to go with it to make up for the -3 of phosphate ion.