Law of Constant Proportions

A liquid compound $\mathrm{X}$ of molecular mass $18 \mathrm{u}$ can be obtained from a number of natural sources. All the animals and plants need liquid $\mathrm{X}$ for their survival. When an electric current is passed through $200 \mathrm{grams}$ of pure liquid $\mathrm{X}$ under suitable conditions, then $178 \mathrm{grams}$ of gas $\mathrm{Y}$ and $22 \mathrm{grams}$ of gas $\mathrm{Z}$ are produced. Gas $\mathrm{Y}$ is produced at the positive electrode whereas gas $\mathrm{Z}$ is obtained at the negative electrode. Moreover, gas $\mathrm{Y}$ supports combustion whereas gas $\mathrm{Z}$ burns itself causing explosions. 

Which law of chemical combination is illustrated by this example?

When $5 \mathrm{g}$ of calcium is burnt in $2 \mathrm{g}$ of oxygen, then $7 \mathrm{g}$ of calcium oxide is produced. What mass of calcium oxide will be produced when $5 \mathrm{g}$ of calcium is burnt in $20 \mathrm{g}$ of oxygen? Which law of chemical combination will govern your answer? 

Magnesium and oxygen combine in the ratio of $3:2$ by mass to form magnesium oxide. What mass of oxygen gas would be required to react completely with $24 \mathrm{g}$ of magnesium? 

In an experiment, $4.90 \mathrm{g}$ of copper oxide was obtained from $3.92 \mathrm{g}$ of copper. In another experiment, $4.55 \mathrm{g}$ of copper oxide gave, on reduction, $3.64 \mathrm{g}$ of copper. Show with the help of calculations that these figures verify the law of constant proportions.

In hydrogen peroxide (H₂O₂), the proportion of hydrogen and oxygen by mass is: 

In water, the proportion of oxygen and hydrogen by mass is :

Which of the following elements has the same molecular mass as its atomic mass?

If $1.4 \mathrm{g}$ of calcium oxide is formed by the complete decomposition of calcium carbonate, then the amount of calcium carbonate taken and the amount of carbon dioxide formed will be respectively: 

State the law of conservation of mass. Give one example to illustrate this law.

In water, the proportion of oxygen and hydrogen is _____ by mass. 

A : $1:4$

B : $1:8$

C : $8:1$

Enter your correct answer as A, B or C.

'If 100 grams of pure water taken from different sources is decomposed by passing electricity, 11 grams of hydrogen and 89 grams of oxygen are always obtained' which chemical law is illustrated by this statement?

Name the law of chemical combination which was given by Proust.

Name the scientist who gave law of constant proportions.