Atoms and Molec...

How many moles of magnesium phosphate, $$Mg_3(PO_4)_2$$ will contain 0.25 mole of oxygen atoms ? 

Number of atoms in 558.5 g of Fe:

The ratio of unpaired electrons present in d orbitals of $$Co^{2+}$$ and $$Cr^{3+}$$Co2+ is ____.

Specific volume of cylindrical virus particles is $${ 6.02\quad \times  }{ 10 }^{ -2 }$$ cc/gm whose radius and length are 7 $$\mathring A$$ and 10 $$\mathring A$$, respectively. If $${ N }_{ A }=6.02\times\  { 10 }^{ 23 }$$ find molecular weight of virus.

If 10$$^{21}$$ molecules are removed from 200 mg of CO$$_{2}$$, the number of moles of CO$$_{2}$$ left is :

If we assume that one-sixth the mass of an atom of $$^{12}C$$ isotope is taken as the reference, the mass of one molecule of oxygen will:

How many oxygen atoms will be present in $$88\  g$$ of $$CO_2$$?

How many grams of $$CaO$$ are required to react with $$852\ g$$ of $$P_4O_{10}$$ according to below given reaction:
$$6CaO+P_4O_{10}\to 2Ca_3(PO_4)_2$$

P and Q are two elements which form $${ P }_{ 2 }{ Q }_{ 3 }$$ and $${ PQ }_{ 2 }$$. If 0.15 mole of $${ P }_{ 2 }{ Q }_{ 3 }$$ weight 15.9 g and 0.15mole of $${ PQ }_{ 2 }$$ weight 9.3 g. what are atomic weights of P and Q respectively?

Who first gave the concept of 'atom'?