1. Interconversions and Stoichiometry
But First:

2. Conversions So far, we have learned to convert between: Moles
Particles (molecules, formula units, atoms)
Mass (g)
Volume (L)
Conversions

3. Interconversions We have also looked at converting:
Between moles of reactants and products (from a balanced chemical equation)
Between molecules of reactants and products
Between volumes of reactants and products (if all are gases)
Interconversions

4. Turns out, we can relate the reactants of a chemical reaction to the products by mass as well!
Law of the Conservation of Mass:
During a chemical reaction, the total mass of the reactants is always equal to the total mass of the products.
Mass Relationship

5. Nitrogen gas reacts with oxygen gas to yield ammonia gas
N2(g) + 3H2(g)  2NH3(g) +
1 molecule N2
1 mol N2(q)
22.4 L N2(g)
28 g N2(g)
3 molecules H2(g)
3 mol H2(g)
67.2 L H2(g)
6 g H2(g)
2 molecule NH3(g)
2 mol NH3(g)
44.8 L NH3(g)
34 g NH3(g) + =
Interconversions

6. Nitrogen gas reacts with oxygen gas to produce nitrogen monoxide
Write the balanced chemical equation and describe the reaction in terms of:
A) moles
B) molecules
C) volume
D) mass
Try it

7. The study of the relative quantities of reactants and products in chemical reactions
Gravimetric stoichiometry: analysis involving mass
Gas stoichiometry: analysis involving volume of gases
Stoichiometry

8. Stoichiometry Need the double Y diagram
Essentially the same type of conversions we have been doing, but now we are converting between different compounds
Need to use the mole ratio!
Mole Ratio
Stoichiometry

9. Carbon dioxide reacts with lithium hydroxide according to the following equation:
CO2(g) + 2LiOH(s)  Li2CO3(s) + H2O(g)
What mass of LiOH is required to react with 1000g of CO2?
Mole Ratio
Example

10. Example: Cont. CO2(g) + 2LiOH(s)  Li2CO3(s) + H2O(g)
Given: 1000 g CO2
Therefore, 1090g of LiOH would be required to
react with 1000g of CO2.
Example: Cont.

11. General Steps 1. Write the balanced chemical equation.
2. If you are given the mass, volume, or number of particles of a substance convert it to moles.
3. Use the mole ratio to calculate the number of moles of the required substance from the moles of the known substance.
4. If required, convert the moles of the required substance to mass (g), volume (L) or number of particles.
General Steps