Unit 3 Topic 5

Chemical Reactions Chemical reactions can be described by writing balanced chemical equations A balanced chemical equation shows the formulas of both the reactants (what you start with) and the products (what was made), the mole ratio of how they interact and their physical states

Products and Reactants The reactants are placed on the left-hand side of the reaction arrow And the products are placed on the right-hand side of the reaction arrow Reactants  Products

Balancing Balanced chemical equations must have the same number of each type of element on each side of the reaction arrow Mass is conserved because the number of atoms is conserved (the same on both sides) It is extremely important to be able to correctly interpret chemical equations.

Coefficients vs Subscripts BIG number small number Multiplies the whole compound after the number Multiplies just the element before the number 5CO H2O

What does this mean? The amount of matter we start with is the same amount of matter we finish with. Source: http://www.tea.state.tx.us This reaction shows 2 compounds combining to form 2 new compounds, however their masses did not change! The same atoms are all there, they have just rearranged themselves.

CaCl2 + Na2SO4  CaSO4 + NaCl

CaCl2 + Na2SO4  CaSO4 + NaCl CaCl2 Na2SO4 CaSO4 NaCl Ca Cl N S O

CaCl2 + Na2SO4  CaSO4 + NaCl 1 2 4 CaCl2 Na2SO4 CaSO4 NaCl Ca Cl Na S

CaCl2 + Na2SO4  CaSO4 + NaCl Calcium is balanced Need more Chlorine on the right Add another NaCl Recheck Chlorine is balanced Sodium is balanced Sulfur is balanced Oxygen is balanced

CaCl2 + Na2SO4  CaSO4 + NaCl 1 CaCl2 + 1 Na2SO4  1 CaSO4 + 2 NaCl

H2O(l) + Fe(s)  Fe3O4(s) + H2 (g)

H2O(l) + Fe(s)  Fe3O4(s) + H2 (g) 1 4 Fe 3

Is this equation balanced? NO! In order to balance the reaction we need to place coefficients in front of each substance in order to make the number of each element the same

Coefficients Are the Hydrogen’s balanced? Are the Oxygens’s balanced? H2O(l) + Fe(s)  Fe3O4(g) + H2 (g) H O Fe Are the Hydrogen’s balanced? YES, both sides have 2 Are the Oxygens’s balanced? NO, left side has 1 right side has 4 WHAT ARE WE GOING TO DO ABOUT IT?

Use Coefficients to BALANCE Next you have to represent the number of compounds with a coefficient in front 4 H2O(l) + Fe(s)  Fe3O4(g) + H2 (g) O Fe H H Fe Fe O O H Fe H O Fe H O O H O To add more Oxygen to the left, you have to add more of the entire compound H O H

Use Coefficients to BALANCE 4 4 H2O(l) + Fe(s)  Fe3O4(g) + H2 (g) O Fe H H Fe Fe O O Fe H H O Fe H H O O H H H O H Next you have to represent the number of SETS with a coefficient in front H H Now the Hydrogens need more on the right, so add 4 more Hydrogens to that side H H O H H

Use Coefficients to BALANCE 4 3 4 H2O(l) + Fe(s)  Fe3O4(g) + H2 (g) O Fe H H Fe Fe O O Fe H H O Fe Fe H H O O H H Fe H H O H Then use a coeffient to represent the number of iron SETS H Next, the irons need to be balanced out by adding 2 more to the left side. H H O H H

When you finish with the Legos Complete Page 11 and show Mrs. Liller for credit. Next complete pages 12 and 13. What you don’t finish do for homework. Balancing Quiz Friday 11/14 I need to see page 7 and 8 from: Derrick Hevert James William

Balancing Reaction Cards (Lab section) Use the legos to create a balanced reaction and write out the equation using the coefficients. Example: H2 O2 H2O + H2O H2 2H2 + O2  2H2O