ChemistryStoichiometry – Ideal Calculationsp. 1

Name:Date: KEY

09.02.1a / Stoichiometry: Ideal Calculations

Purpose

The purpose of this activity is tocalculate the moles and/or mass of a reactant or product in a chemical reaction.

Background

We use stoichiometric calculations when one wants to calculate the amount of product formed by a chemical reaction, or the amount of a reactant needed in a chemical reaction.

For example, how many grams of water can be made from 100.g of hydrogen gas? We use dimensional analysis is used to solve stoichiometric calculations!

Model

Question: How many grams of water can be made from 100.g of hydrogen gas?(Assume an unlimited supply of oxygen gas.)

Steps.

  1. Write the balanced chemical equation.

2H2 + 1O22H2O

  1. Identify:
  2. What you know (where you are starting)...... 100. g H2
  3. What you want to know (where you want to end)...... X g of water
  1. Set up the skeletal dimensional analysis equation:

100. g H2x ------= X g H2O

  1. Identify the conversion factor. This allows you to change the units from the known to the unknown substance. The most common conversion factor in stoichiometric calculations is mass-to-mass of different chemicals. E.g., mass H2 mass H2O). Sometimes, you may need to convert between mass, moles, volume, and particles (atoms or molecules). ALL stoichiometric calculations go throughmolesA to molesB.
  1. The unit in the denominator for the first step is the same as the unit you start with.
  1. Convert this to the conversion factor units: g H2 mol H2.
  1. Fill in all of the other values and units needed. Make sure all of the units cancel out except the one you want in the answer.
  1. Perform the calculations.
  1. Check:

H2 is much lighter than H2O, so the mass of H2O should be less.

Problems

Directions: Complete all the steps shown in the model problem above when you write your answers with the correct units and significant figures.

  1. HW 7-1 Read Sections 9-1 and 9-2 Questions 1-2 Page 305

  1. How many grams of lithium oxide can be produced from 32.04 g of lithium and an unlimited amount of oxygen?

  1. What mass of sodium chloride is produced when chlorine reacts with 0.29 g of sodium?

  1. Determine the mass of carbon dioxide produced when 0.850 g of butane (C4H10) burns.

  1. Hydrogen reacts with oxygen in a synthesis reaction to make water. If you have 2.99 g of oxygen how many grams of hydrogen do you need?

  1. Lead (II) oxide reacts with hydrochloric acid in a double displacement reaction. How many grams lead (II) chloride will be produced if you have 0.79 g of lead(II) oxide?

  1. Hydrochloric acid and 50.0 grams of iron(III) sulfide react. What mass of dihydrogenmonosulfide gas is produced?

  1. How many grams of nitric acid is needed to react completely with 25.0 grams of magnesium in a single replacement reaction?