How many grams of NH3 can be produced from 3.24 mol of N2 and excess H2. Express your answer numerically in grams.

How many grams of H2 are needed to produce 12.61 g of NH3?
Express your answer numerically in grams.

How many molecules (not moles) of NH3 are produced from 2.12×10−4 g of H2?
Express your answer numerically as the number of molecules.

Since the molar ratio of N2 to Nh3 is 2:1, you can make twice as much NH3 by using N2.

Therefore, you can make a maximum of 4.5 mol of NH3 assuming 100% yield.

Explanation:

1) First, recognize that whenever we are reacting molecules with each other and want to calculate an amount of end product, we will need to know the ratios between the reactants and the products. This will help in our conversion from amount of reactant to amount of product. We do this through a balanced equation.

__N2  + __H2  ->  __NH3

If we start with 1 next to the N2 (and we can always change that later!), there are 2 N's on the reactant (left) side, so place a 2 next to the NH3 to make 2 total N's on the products (right) side.

1 N2 + 3 H2 ->  2 NH3

Now there are 6 H's on the left side but only 2 on the products side. So, add a 3 ahead of the H2 to balance the H's.

2) Second, reread the question. In the question, it notes that there is an excess of H2. From this, we know that N2 is the limiting reactant. Whenever the N2 is used up, we are done reacting.

From our balanced equation, we know that we make 2 molecules of NH3's for each 1 molecules of N2 that reacts. For 2.25 mol of N2, we will get 4.50 mol NH3. I like to set things up as fractions so the units in the numerator and denominator cancel just to be sure I've written my ratios correctly to multiple or divide.

2.25 mol N2 * (2 mol NH3 / 1 mol N2) = 2.25 * 2 / 1 = 4.50 mol NH3

3) Reread the question again. Are these the units we have been asked for? The question asks to put the answer into grams, so we need to convert the mol NH3 to g NH3. We do this using the molar mass.

Add up the molar masses (listed on the periodic table) for each of the atoms to get the molar mass for the molecule.

Molar mass of N = 14.01 g/mol

Molar mass of H = 1.008 g/mol

Molar mass of NH3 = 1 * 14.01 g/mol + 3 * 1.008 g/mol = 14.032 g/mol

Then convert the mol NH3 to g by multiplying by the molar mass. Again, I like to write everything out as fractions to make sure I am multiplying or dividing correctly.

4.50 mol NH3 * (14.032 g NH3 / 1 mol NH3) = 63.144 g NH3

there are two significant figures.

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