Chemical Equations. Their Job: Depict the kind of reactants and products and their relative amounts in a reaction.

Transcription

1 Chemical Equations Their Job: Depict the kind of reactants and products and their relative amounts in a reaction.

2 Balancing Equations Law of Conservation of Matter: In a chemical reaction, matter can be neither created nor destroyed. In a chemical reaction, the amount of reactants equal the amount of products.

3 Balancing Equations Paraphrase: Law of Conservation of Atoms: The number of atoms of each type of element must be the same on each side of the equation.

4 Phases In most cases, phases must also be written. You should always include symbols for reactions you observe in the laboratory! Solid ex: Cu (s) Liquid ex: H 2 O (l) Gas ex: Cl 2(g) Aqueous ex: NaCl (aq)

5 Aqueous Means solutions Made of water and something dissolved in water

6 Hydrogen gas combined with Oxygen gas will produce Dihydrogen Monoxide liquid H 2 + O 2 H 2 O Should be: H 2(g) + O 2(g) H 2 O (l)

7 BUT, matter is always conserved, atoms must be conserved!!!!!!!! In order to make water, there needs to be 2 hydrogen molecules for every 1 oxygen molecule. 2 H 2 (g) + O 2 (g) 2 H 2 O(l)

8 A + sign separates molecules on the same side The arrow is read as yields, forms, produces, etc. Example C + O 2 CO 2 This reads carbon plus oxygen react to yield carbon dioxide

9 WE MUST BALANCE!!! To correctly write and balance an equation: 1. Formulas MUST be correct 2. There must be the same number of each kind of atom on each side of the arrow. This is done by using coefficients (numbers in front of a formula). 3. Do not change formulas to balance atoms!! 4. Follow a trial and error process. Balance each species one at a time. Be prepared to erase!!

10 Balancing simple equations LiCl Li + Cl 2 1 Li 1 Li 1 Cl 2 Cl 2LiCl Li + Cl 2 2 Li 1 Li 2 Cl 2 Cl 2LiCl 2Li + Cl 2 2 Li 2 Li 2 Cl 2 Cl BALANCED!

11 Balancing simple equations K + Cl 2 KCl 1 K 1 K 2 Cl 1 Cl K + Cl 2 2 KCl 1 K 2 K 2 Cl 2 Cl 2K + Cl 2 2 KCl 2 K 2 K 2 Cl BALANCED!!!!!!!!!!!!!!!! 2 Cl

12 Balancing simple equations NaN 3 Na + N 2 1 Na 1 Na 3 N 2 N 2 NaN 3 Na + 3 N 2 2 Na 1 Na 6 N 6 N 2 NaN 3 2 Na + 3 N 2 2 Na 2 Na 6 N 6 N BALANCED!

13 Balancing simple equations Fe + O 2 Fe 2 O 3 1 Fe 2 Fe 2 O 3 O 2Fe + O 2 Fe 2 O 3 2 Fe 2 Fe 2 O 3 O 2Fe + 3O 2 2Fe 2 O 3 2 Fe 4 Fe 6 O 6 O 4Fe + 3O 2 2Fe 2 O 3 4 Fe 4 Fe 6 O 6 O BALANCED

14 NiO + Al Al 2 O 3 + Ni 1 Ni 1 Ni 1 O 3 O 1 Al 2 Al NiO + 2 Al Al 2 O 3 + Ni 1 Ni 1 Ni 1 O 3 O 2Al 2 Al 3 NiO + 2 Al Al 2 O 3 + Ni 3 Ni 1 Ni 3 O 3 O 2 Al 2 Al 3 NiO + 2 Al Al2O3 + 3 Ni 3 Ni 3 Ni 3 O 3 O 2 Al 2 Al BALANCED

15 C 4 H 8 + O 2 CO 2 + H 2 O 4 C 1 C 8 H 2 H 2 O 3 O C 4 H 8 + O 2 4CO 2 + H 2 O 4 C 4 C 8 H 2 H 2 O 9 O C 4 H 8 + O 2 4CO 2 + 4H 2 O 4 C 4 C 8 H 8 H 2 O 12 O C 4 H 8 + 6O 2 4CO 2 + 4H 2 O 4 C 4 C 8 H 8 H 12 O 12 O

16 Balancing Reactions containing polyatomic atoms Example Li 3 PO 4 + MgCO 3 Li 2 CO 3 + Mg 3 (PO 4 ) 2 1. Keep the polyatomic ions together on both sides 2. Balance the metal ions first, or if they are balanced, the polyatomic ions first, metals last If your formulas are correct, the equation should balance

17 Cu + AgNO 3 Ag + Cu(NO 3 ) 2 1 Cu 1 Cu 1 Ag 1 Ag 1 NO 3 2 NO 3 Cu + 2AgNO 3 Ag + Cu(NO 3 ) 2 1 Cu 1 Cu 2 Ag 1 Ag 2 NO 3 2 NO 3 Cu + 2AgNO 3 2Ag + Cu(NO 3 ) 2 1 Cu 1 Cu 2 Ag 2 Ag 2 NO 3 2 NO 3 Balanced

18 Ca(C 2 H 3 O 2 ) 2 + K 2 CO 3 CaCO 3 + KC 2 H 3 O 2 1 Ca 1 Ca 2 C 2 H 3 O 2 1 C 2 H 3 O 2 2 K 1 K 1 CO 3 1 CO 3 Ca(C 2 H 3 O 2 ) 2 + K 2 CO 3 CaCO 3 + 2KC 2 H 3 O 2 1 Ca 1 Ca 2 C 2 H 3 O 2 2 C 2 H 3 O 2 2 K 2 K 1 CO 3 1 CO 3

19 Balancing Equations Balancing hints: Balance the metals first. Balance the polyatomic ion groups next. Balance the other atoms. Save the non polyatomic ion group hydrogen(2 nd to last) and oxygen (very last)

20 Word equations (writing equations from observations) Water is decomposed by electricity to produce hydrogen and oxygen gases through a process called electrolysis. When copper(ii)chloride is dissolved in water and reacts with aluminum metal, copper metal and an aluminum chloride solution is produced.

21 Lead(II)nitrate solution reacts with sodium sulfate solution to produce lead(ii)sulfate solid and sodium nitrate solution. Aluminum iodide solution reacts with lithium hydroxide solution to produce aluminum hydroxide solid and lithium iodide solution.

22 tetracarbon decahydride (butane) gas reacts with oxygen gas to produce carbon dioxide gas and water vapor. Ammonia gas reacts with oxygen gas to produce nitrogen gas and liquid water.

23 Remember the following: 1. Diatomic elements hydrogen gas, nitrogen gas, oxygen gas AND all halogens in their elemental form 2. The formulas and charges of the polyatomic ions

24 WOW The key is that Formulas MUST be correct and there must be the same number of each kind of atom on each side of the arrow. Now go be reactive and produce some good work. Assignment is: (depending on how well you work)