Balancing Hydrocarbons

Transcription

1 Balancing Equations a. Add coefficients to make atoms the same on both sides b. Must balance Metals first, then Nonmetals, followed by Hydrogen, and Oxygen last ( met nine hairy oxen ) c. Adjust totals to account for the addition of your coefficient d. Continue to add coefficients and make adjustments until all elements are balanced

2 Balancing Hydrocarbons 1. Divide H subscript by 2. IF it is odd or a fraction, then multiply the hydrocarbon by IF it is not odd, do not multiply by 2, but go to step Then balance in the order C, H, O, and lastly O 2 Oleic Acid C 18 H 34 O O 2 34H 2 O(g) + CO 2 (g) 2 36 Propionic Acid C 3 H 6 O O 2 6H 2 O(g) + CO 2 (g) 2 6

3 Chemical Reactions

4 Chemical Reaction a process in which a substance(s) is changed into one or more new substances

5 Chemical Equation uses chemical symbols to show what happens during a chemical reaction; standard way of representing chemical reactions; chemists shorthand description of a reaction

6 Chemical Symbols 1. + = reacts with, and, can combine 2. = to produce, yield, to form; the reaction is assumed to proceed from left to right as the arrow indicates 3. = heat 4. Subscript = tells how many atoms of an element are present (smaller and to the right of the number) 5. Coefficient = multiplier (larger number to the left of the number)

7 Chemical Symbols 6. Physical states a. (s) solid b. (l) liquid c. (g) gas d. (aq) aqueous - (dissolved in water)

8 Balanced Chemical Equations After writing a skeleton equation: to conform with the law of conservation of mass, there must be the same number of each type of atom on both sides of the arrow we must have as many atoms after the reactions ends as we did before it started to balance a chemical equation place coefficients in front of reactants and/or products

9 Chemical Equations Reactants with to produce or yield 2 H 2 (g) + O 2 (g) 2 H 2 O (l) Reactants Product(s)

10 Interpretation 2 H 2 + O 2 2 H 2 O Two molecules + One molecule Two molecules 2 moles + 1 mole 2 moles 2(2.02 g) g 2 (18.02 g) g reactants g product

11 Reactants and Products 1. Reactants starting materials in a chemical reaction; written on the left of the arrow 2. Products substance formed as a result of a chemical reaction; written on the right of the arrow

12 Evidence Temperature change Color change Odor Gas/bubbles Appearance of a solid (precipitate) **difference in composition before and after

13 Types of Reactions Synthesis (or Combination) Two or more substances react to produce a single product

14 Decomposition + A single compound breaks down into two or more new elements or compounds

15 Single-replacement (or single-displacement) + + Like a girlfriend thief atoms of one element replace the atoms of another element in a compound

16 Double-replacement (or double-displacement) Like Wife Swap When there is an exchange of ions between compounds

17 Combustion -a substance combines with oxygen (O 2 ) and releases energy -Oxygen is always a reactant! Hydro carbon 2H 2(g) + O 2(g) 2H 2 O (g) + O 2(g) CO 2 (g) + H 2 O(g)

18 Use S, D, SR, DR or C for abbreviations Mg + O 2 MgO C S Al 2 O 3 Al + O 2 D CuCl 2 + H 2 S CuS + HCl DR Cl 2 + NaBr NaCl + Br 2 SR CH 4 + O 2 CO 2 + H 2 0 C

19 Reactions Key H 2 O = liquid (l) unless told other state of matter solution = aqueous = (aq) gas or vapor = (g) metal, powder, particles or solid = (s) heat, burned =

20 Skeleton Equations Skeleton equations are not balanced using coefficients It is a translation from words to formulas only Most times states of matter are given in the words stated

21 Skeleton Equation (not balanced) Sodium metal = Na(s) Reacts with = + Water = H 2 O(l) (use l for water unless you know it forms a gas or solid) Forming = Sodium hydroxide solution = NaOH (aq) (aq because it said solution) Hydrogen gas = H 2 (g) Na(s) + H 2 O(l) NaOH (aq)+ H 2 (g)