PLEASE HELP..... Converting between quantities To convert from a given quantity

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PLEASE HELP.....

Converting between quantities

To convert from a given quantity of one reactant or product to the quantity of another reactant or product:

First, convert the given quantity to moles. Use molar masses to convert masses to moles, and use Avogadro's number (6.02×1023 particles per mole) to convert number of particles to moles.

Next, convert moles of the given reactant or product to moles of the desired reactant or product using the coefficients of the balanced chemical equation. For example, in the chemical equation

2H2+O22H2O

the coefficients tell us that 2 mol of H2 reacts with 1 mol of O2 to produce 2 mol of H2O.

Finally, convert moles of the desired reactant or product back to the desired units. Again, use molar masses to convert from moles to masses, and use Avogadro's number to convert from moles to number of particles.

Reaction of hydrogen and nitrogen to form ammonia

Hydrogen gas, H2, reacts with nitrogen gas, N2, to form ammonia gas, NH3, according to the equation

3H2(g)+N2(g)2NH3(g)

NOTE: Throughout this tutorial use molar masses expressed to five significant figures.

Part A

How many moles of NH3 can be produced from 21.0 mol of H2 and excess N2?

Express your answer numerically in moles.

Part B

How many grams of NH3 can be produced from 4.57 mol of N2 and excess H2.

Express your answer numerically in grams.

Part C

How many grams of H2 are needed to produce 13.53 g of NH3?

Express your answer numerically in grams.

Part D

How many molecules (not moles) of NH3 are produced from 7.53×104 g of H2?

Express your answer numerically as the number of molecules.

Part C

How many grams of H2 are needed to produce 13.53 g of NH3?

Express your answer numerically in grams.

Part D

How many molecules (not moles) of NH3 are produced from 7.53×104 g of H2?

Express your answer numerically as the number of molecules.

Explanation / Answer

3H2(g)+N2(g)2NH3(g)
3 moles of H2 produces 2 moles of NH3
21 moles of H2 produces 2/3*21 moles of NH3
                        = 14 moles of NH3
1 mole of N2 produces 2 moles of NH3
4.57 moles of N2 produces 2 * 4.57
                        = 9.14 moles of NH3

mass of NH3 = 9.14 * 17 g = 155.38 g of NH3
2 moles of NH3 require 3 moles of H2
2 * 17g of NH3 require 3 * 2g of H2
13.53 g of NH3 require (3*2/2*17) * 13.53 g of H2
                      = 2.3876 g of H2
3*2 g of H2 produces 2*17 g of NH3
7.53 *10^-4 g of H2 produces 2 * 17/(3*2)*7.53 *10^-4 g of NH3
                           = 4.267*10^-3 g of NH3
moles of NH3 = 4.267*10^-3 / 17 = 2.51*10^-4 moles
number of molecule = 2.51 * 10^-4 * 6.023 * 10^23 = 1.5117 * 10^20 molecules

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