Which law states that during any chemical or physical change, the total mass of the products obtained is always equal to the total mass of reactants taken at the beginning of the change ?

Which law says that when two elements combine separately with a definite mass of a third element, then the ratio of their masses in which they do so is either the same or some whole number multiple of the ratio in which they combine with each other ?

What is the weight of oxygen required for the complete combustion of 2.8 kg of ethylene ?

Which law states that, when two elements combine to form two or more compounds, then the different masses of one element, which combine with a fixed mass of the other element, bear a simple whole number ratio with one another ?

Assuming fully decomposed, the volume of CO₂ releases at STP on heating 9.85 g of BaCO₃ (atomic mass, Ba = 137) will be

The percentage weight of Zn in white vitriol [ZnSO₄ . 7 H₂O] is approximately equal to  (Zn = 65, S = 32, O = 16 and H = 1 )

The species of an atom which possess different relative masses are called

Boron has two stable isotopes, .  Calculate average atomic weight of boron in the periodic table.

A metal oxide has the formula Z₂ O₃ .  It can be reduced by hydrogen to give free metal and water.  0.1596g of the metal oxide requires 6 mg of hydrogen for complete reduction.  The atomic weight of the metal is

Which law says , a chemical compound, no matter from which source it is obtained, always contains the same elements combined together in the same definite proportion by mass ?