A 20.9 g sample of nitrogen gas combines completely with 4.5 g of hydrogen gas to form ammonia. What is the mass of ammonia formed?

A 12.7 g sample of X combines with a 24.4 g sample of Y to form the compound XY2. What is the mass of the reactants?

A. what is 20.9+4.5 g?

b. X mass given, as is y mass. Those are the masses of the reactants.

To find the mass of ammonia formed in the first question, we need to use the concept of stoichiometry. Stoichiometry is the calculation of the quantities of reactants and products involved in a chemical reaction.

First, we need to determine the balanced chemical equation for the reaction between nitrogen gas (N2) and hydrogen gas (H2) to form ammonia (NH3).

The balanced equation is:

N2 + 3H2 -> 2NH3

According to the balanced equation, 1 mole of nitrogen gas reacts with 3 moles of hydrogen gas to produce 2 moles of ammonia.

To calculate the moles of nitrogen gas, we can use its molar mass, which is 28.01 g/mol:

moles of nitrogen gas = mass of nitrogen gas / molar mass of nitrogen gas
= 20.9 g / 28.01 g/mol
≈ 0.746 mol

Similarly, we can calculate the moles of hydrogen gas using its molar mass, which is 2.02 g/mol:

moles of hydrogen gas = mass of hydrogen gas / molar mass of hydrogen gas
= 4.5 g / 2.02 g/mol
≈ 2.228 mol

Since nitrogen gas and hydrogen gas are in a 1:3 ratio, the limiting reactant is the nitrogen gas because it has fewer moles (0.746 mol) compared to the hydrogen gas (2.228 mol).

Now, we need to find the moles of ammonia formed using the stoichiometry ratio:

moles of ammonia = (moles of nitrogen gas) * (moles of ammonia / moles of nitrogen gas)
= 0.746 mol * (2 mol NH3 / 1 mol N2)
= 1.492 mol NH3

Finally, we can calculate the mass of ammonia formed using its molar mass, which is 17.03 g/mol:

mass of ammonia = moles of ammonia * molar mass of ammonia
= 1.492 mol * 17.03 g/mol
≈ 25.37 g

Therefore, the mass of ammonia formed is approximately 25.37 g.

In the second question, to find the mass of the reactants (X and Y) in the compound XY2, we need to know the molar masses of X and Y or have additional information about their composition and properties. Without more information, we cannot calculate the exact mass of the reactants.