Which law explains why 18g of water always decomposes into 2g of hydrogen and 16g of oxygen?

A sample of hydrated copper sulfate ($CuSO_4 \cdot xH_2O$) weighs 25 g. Upon heating to drive off all the water, the anhydrous copper sulfate ($CuSO_4$) remaining weighs 16 g. What is the value of 'x' (the number of water molecules of crystallization)?

Two different samples of copper(II) oxide were analyzed and found to contain the same percentage of copper by mass. Which law does this illustrate?

Hydrogen and oxygen combine to form water (H2O). If 4g of hydrogen reacts completely with oxygen to form water, what mass of oxygen is required?

Which law explains the observation that 1g of hydrogen always combines with 8g of oxygen to form 9g of water?

Which of the following reactions is the metal displacement reaction? Choose the right option.

Which law explains why 18g of water always decomposes into 2g of hydrogen and 16g of oxygen?

If two elements A and B combine in different ratios to form two compounds, the masses of B that combine with a fixed mass of A are in a small whole number ratio. This is a statement of:

Which of the following reactions is the metal displacement reaction? Choose the right option.

Two elements X and Y combine to form two compounds $XY_2$ and $X_2Y_3$. If 0.05 moles of $XY_2$ weighs 5 g and 0.10 moles of $X_2Y_3$ weighs 20 g, find the atomic masses of X and Y.

Which of the following reactions is not correct according to law of conservation of mass