1. A balanced chemical equation allows one to determine the mole ratio of any two substances in the reaction.
2. The coefficients in a chemical equation represent the relative number of moles of reactant and product.
3. Fewer steps are required to solve stoichiometry problems when the reactant is given in moles and
the product is sought in moles.
4. If you know the mole ratio of a reactant and product in a chemical reaction, you can calculate the
mass of the product produced from the known mass of the reactant.
5. A + B yields C + D
If one knows the mass of A and the molar mass of product D in a chemical reaction, one can determine
the mass of product D produced by using the mole ratio of D to A from the chemical equation.
6. In a chemical reaction WA + XB yields YC + ZD, a comparison of the number of moles of A to the
number of moles of C would be a mole ratio.
7. In the chemical equation WA + XB yields YC + ZD, if one knows the mass of A and the molar masses
of A,B,C and D one can determine the mass of any of the reactants or products.
8. The reactant that controls the amount of product formed in a chemical reaction is called the limiting reactant.
9. The chemical reaction involving substances A and B stops when B is completely used.
10. When the limiting reactant in a chemical reaction is completely used, the reaction stops.
11. In the reaction A + B yields C + D, if the quantity of B is insuffcient to react with all of A, B is
the limiting reactant.
12. The substance that restricts the participating of other reactants in a chemical reaction is known
as the limiting reactant.
13. The substances not completely used up in a chemical reaction is known as the excess reactant.
14. When a chemical reaction is performed in industry the least expensive and most abundant chemical
is often chosen as the excess reactant.
15. To determine the limiting reactant in chemical reaction, one must know the available amount of each reactant.
16. The % yield is the ratio of the actual yield to the theoretical yield, multiplyed by 100.
17. The actual yield is the measured amount of a product obtained from a chemical reaction.
18. In most chemical reactions, the amount of product obtained is less than the theoretical yield
% yield = actual / theoretical * 100
19. The theoretical yield is the maximum possible amount of product obtained in a chemical reaction.
20. Actual yield must be determined by experiments.
21. Actual yield of a chemical reaction is less than theoretical yield.
Gas samples at STP - standard temperature and pressure
Sample 1 Sample 2 Sample 3 Sample 4
16g oxygen 28g nitrogen 8g hydrogen 142g chlorine
22. Sample 3 occupies the greatest volume.
23. The ratio of number of particles in sample 1 and 2 is twice as many nitrogen paricles as oxygen particles.
24. 32 grams of oxygen will contain the same number of particles as the sample of nitrogen in the figure above.
25. Sample 3 contains the greatest number of particles.
26. If sample 3 and 4 react, the chemical reaction is as follows: H2 + Cl2 yields 2HCl
27. The excess reactant will be H2 and the limiting reactant will be Cl2 because:
excess reactant 8 g H2 / 1 * 1 mol H2 / 2g H2 * 2 mol HCl/ 1 mol H2 = 8 mol HCl
limiting reactant 142g Cl2 /1 * 1 mol / 71g Cl2 * 2 mol HCl / 1 mol Cl2 = 4 mol HCl
28. If sample 3 and 4 react with each other, sample 4 would be the limiting reactant.
29. To leave no excess reactant, 5 moles of sample 3 are needed to react with 5 moles of sample 4.
30. 10 moles of hydrogen were available initially if 4 moles of hydrogen chloride were found in the
mixture of gases at the end of the reaction. 8 moles of hydrogen remain.