It seems like I keep on asking for more help...
1)Some fertilisers are labelled "NPK fertiliser" because they contain the elements nitrogen, phosphorus and potassium. Which of the following pairs of compounds could be used as a "NPK fertiliser"?
A) ammonia and sodium hydrogen phosphate
B) ammonium phosphate and calcium sulfate
C) calcium phosphate and potassium nitrate
D) potassium hydrogen phosphate and calcium sulfate
the answer is C but I'm not sure why...please explain
2) A red powder is placed in a test tube, water is added and the contents are then filtered. A brown solid is left on the filter paper. After evaporating the filtrate, white crystals are left. This analysis suggest:
a) the red powder is a mixture
b) the brown solid is an element
c) the white crystals are a mixture
d) the red powder is a compound
a?
3) Atom X has two electrons in it's outer shell while atom Y has seven. The chemical formula of the compound formed from X and Y would be:
a) X^2Y^6
b) X^2Y
c) X^2Y^2
d) XY^2
4) identify the group in which all of the substances have covalent bonds:
a) diamond, graphite, carbon dioxide, potassium fluoride
b) hydrogen iodide, water, calcium chloride, paraffin wax
c) iodine, ice, zinc sulfide, ethanol
d) ammonia, oxygen, water, methane