1. Chemical Reactions Quiz Preparation
Photo Credit: Richard Megna/Fundamental Photographs

2. Chemical Reactions rearrange atoms to form new molecules.
No atoms (lego) are created or destroyed, they only get rearranged.

3. Chemical Reactions rearrange atoms to form new molecules.
Reactants: the molecules you began with. (the molecules that reacted together)
Products: the molecules you end up with. (the molecules that are produced)
reactants  products

4. Law of conservation of matter:
Atoms are never created or destroyed in chemical reactions.
(they just get rearranged into new molecules).
IOW: (in other words) The number of atoms on the products side of a reactions will be exactly the same as the number of atoms found on the reactants side of the reaction.

5. This reaction has obeyed the Law of Conservation of matter. LOCOM
Carbon dioxide Water Carbonic Acid
CO H2O  H2CO3
Reactants Products---
C O O + H H O  H H C O O
6 atoms
(the Reactant side)
6 atoms
(product side)
This reaction has obeyed the
Law of Conservation of matter. LOCOM

6. O2 + 2H2  H2O + H2O OO + HH HH  HHO HHO
All the equations we use will be correctly balanced and obey the LOCOM
O H2  H2O + H2O
These large numbers represent the number of molecules on this side of the reaction.
These small numbers represent the number of atoms in the molecule.
Rewritten to show all atoms
OO + HH HH  HHO HHO

7. O2 + 2H2  2H2O O2 + H2 + H2  H2O + H2O OO + HH HH  HHO HHO
1 oxygen
molecule
2 Hydrogen molecules
2 water
molecules
Rewritten to show all molecules separately:
O2 + H2 + H2  H2O + H2O
Rewritten to show all atoms:
OO HH HH  HHO HHO

8. Did this reaction obey the LOCOM ?
2C2H O2  4CO2 + 6H2O
How many reactant molecules
are there? molecules
How many product molecules
are there? molecules
Did this reaction obey the LOCOM ?
Yes it did, since it is the atoms (not the molecules) that must be the same on both sides.

9. 2C2H6 + 7O2  4CO2 + 6H2O C2H6 C2H6 + O2 O2 O2 O2 O2 O2 O2 
Rewritten to show all molecules:
C2H6 C2H6 + O2 O2 O2 O2 O2 O2 O2 
CO2 CO2 CO2 CO H2O H2O H2O H2O H2O H2O
Rewritten to show all atoms:
CCHHHHHH CCHHHHHH + OO OO OO OO OO OO OO 
COO COO COO COO HHO HHO HHO HHO HHO HHO

10. The same number of atoms are always on both sides = LOCOM
6CO H2O  C6H12O O2
How many reactant molecules? How many product molecules?
12 molecules molecules
Rewritten to show all molecules:
CO2 CO2 CO2 CO2 CO2 CO H2O H2O H2O H2O H2O H2O 
C6H12O O2 O2 O2 O2 O2 O2
Rewritten to show all atoms:
COO COO COO COO COO COO + HHO HHO HHO HHO HHO HHO 
CCCCCCHHHHHHHHHHHHOOOOOO OO OO OO OO OO OO
The same number of atoms are always on both sides = LOCOM

11. Chemical equations handout. And then the chemical equations QUIZ.

13. 1 3

14. 2

15. 6

16. 6

17. 1 16 1 18

18. 1 1 16 16 1 1 36

19. Now try part 2

20. 7

21. 6

22. 18
C C H H
O O
C O O
H H O

23. 18
C C H H
O O
C O O
H H O

24. 26
C C H H
O O
C O O
H H O

25. 44
C C H H
O O
C O O
H H O

26. 212
C C H H
O O
C O O
H H O

27. 212
C C H H
O O
C O O
H H O

28. atoms
molecule
molecules
reaction

29. One last chance to review

30. How many product molecules are there?
2C2H O2  4CO H2O
ethane oxygen carbon dioxide water
How many product molecules are there?

31. How many product molecules are there?
2C2H O2  4CO H2O
ethane oxygen carbon dioxide water
How many product molecules are there? 10

32. How many reactant atoms are there?
2C2H O2  4CO H2O
ethane oxygen carbon dioxide water
How many reactant atoms are there?

33. How many reactant atoms are there?
2C2H O2  4CO H2O
ethane oxygen carbon dioxide water
How many reactant atoms are there?
CCHHHHHH OO 30
Each letter is an atom.

34. How many oxygen atoms are in the products?
2C2H O2  4CO H2O
ethane oxygen carbon dioxide water
How many oxygen atoms are in the products?

35. How many oxygen atoms are in the products?
2C2H O2  4CO H2O
ethane oxygen carbon dioxide water
How many oxygen atoms are in the products?
COO
HHO 14
Only count the “O” (oxygen) atoms

36. What is the mass of 1 ethane molecule?
2C2H O2  4CO H2O
ethane oxygen carbon dioxide water
What is the mass of 1 ethane molecule?

37. What is the mass of 1 ethane molecule?
2C2H O2  4CO H2O
ethane oxygen carbon dioxide water
What is the mass of 1 ethane molecule? 30
C C H H H H H H
= 30

38. What is the mass of all the ethane?
2C2H O2  4CO H2O
ethane oxygen carbon dioxide water
What is the mass of all the ethane?

39. What is the mass of all the ethane?
2C2H O2  4CO H2O
ethane oxygen carbon dioxide water
What is the mass of all the ethane?
C C H H H H H H
= 30
C C H H H H H H
= 30
Total = 60

40. What is the mass of all the products?
2C2H O2  4CO H2O
ethane oxygen carbon dioxide water
What is the mass of all the products?

41. What is the mass of all the products?
2C2H O2  4CO H2O
ethane oxygen carbon dioxide water
What is the mass of all the products?
COO
HHO
1+1+16
284

42. Now you can go and retake the quiz with Mr. Gillam during lunch.