Unbalanced relative molecular masses in reactions?

[tory88]

What is the reason that, in chemical reactions (I.E. between Calcium Carbonate and Hydrocloric Acid) the Relative Molecular Masses are unequal on the left and right side of the equation?

[Sonic]

What is the reason that, in chemical reactions (I.E. between Calcium Carbonate and Hydrocloric Acid) the Relative Molecular Masses are unequal on the left and right side of the equation?

Relative molecular masses are simply relative, the relation of anything compared to 12g/Na [Avagadro's number] of C-12 atoms. Therefore different compounds have different masses - if we were to convert them all to grams by multiplying the molecular mass by the molar amount we see that mass is conserved. Using your example (we will assume there is 1 mole of everything but HCl and 2 moles of HCl as per the equation below)


CaCO3 + 2HCl -----> CaCl2 + CO2 + H2O

Mr: 100 + 2* 38.5---> 115 + 44 + 18

The sum of these is 0 so mass is conserved