Hydrogen and oxygen combine in the ratio of $1:8$ by mass to form water. What mass of oxygen gas would be required to react completely with $3 \,g$ of hydrogen gas (in $,g$)?

State whether the following statement is true or false:
In a chemical substance,the elements are always present in varying proportions by mass.

Name the international organization that approves the names of elements. Give an example with an explanation to show that the Law of Conservation of Mass applies to physical changes as well.

$(a)$ State the law of conservation of mass.
$(b)$ What mass of silver nitrate will react with $5.85 \, g$ of sodium chloride to produce $14.35 \, g$ of silver chloride and $8.5 \, g$ of sodium nitrate,if the law of conservation of mass is true?

State whether the following statement is true or false:
In water,the ratio of the mass of hydrogen to the mass of oxygen is always $1:8$,regardless of the source of water.

Dalton's atomic theory successfully explained which of the following laws?
$(i)$ Law of conservation of mass
$(ii)$ Law of constant composition
$(iii)$ Law of radioactivity
$(iv)$ Law of multiple proportion