Atoms and Molec...

Which of these would support the idea that mass is conserved in a reaction that produces gas as a product?

In a chemical reaction, $100 g$ baking soda mixture containing sodium bicarbonate and vinegar on heating gives $43 g$ of carbon dioxide gas. What mass of solid residue is left in food?

Calculate the molecular mass (u) of Phosphoric Acid ($\displaystyle { H }_{ 3 }{ PO }_{ 4 }$).
$[H=1, P=31, O=16]$

Calculate the formula unit mass (u) of $\displaystyle { CaCl }_{ 2 }$.

Calculate the molecular mass of Nitric acid ($\displaystyle { HNO }_{ 3 }$).

Calculate the molecular mass (u) of Sulphuric acid ($\displaystyle { H }_{ 2 }{ SO }_{ 4 }$).

When $1.375\ g$ of cupric oxide is reduced on heating in a current of hydrogen, the weight of copper remaining $1.098\ g$. In another experiment, $1.179\ g$ of copper is dissolved in nitric acid, and the resulting copper nitrate is converted into cupric oxide by ignition. The weight of cupric oxide formed is $1.476 \ g$. This is in agreement with :

Calculate the molecular mass (u) of $\displaystyle ZnO$.

Which is not one of the laws of chemical combinations?