Reactants Products HCl (aq) + Zn (s) H2 (g) + ZnCl2 (aq)

Transcription

1 Chemical Equation

2 Chemical Equation Includes the substances being reacted (reactants), the substances being formed (products), the phases of each of the substances, the number of moles of each substance, and the resultant energy change. Reactants Products Coefficients are placed in front of the substance symbols to denote a mole ratio that is in accordance with the Law of Conservation of Mass. Cl (aq) + Zn (s) 2 (g) + ZnCl 2 (aq) (reactants) (products) This says that hydrochloric acid reacts with zinc metal to form hydrogen gas and zinc chloride.

3 Word Equations A WORD EQUATION describes chemical change using the names of the reactants and products. Write the word equation for the reaction of methane gas with oxygen gas to form carbon dioxide and water. methane + oxygen carbon dioxide + water Reactant Product + + C 4 2 O 2 CO O

4 Checking for understanding Write the word equation: Zn + Cl ZnCl Ca(O) PO 4 Ca 3 (PO 4 ) O 6Cl + Fe 2 O 3 2FeCl O

5 Click Below for the Video Lectures Symbolic Representation

6 Balancing Equation

7 The Law of Conservation of Mass Mass cannot be created or destroyed by physical or chemical change. The elements found in the reactants can be the only elements found in the products, and there must be equal numbers of moles of those elements on both sides. Cl (aq) + Zn (s) 2 (g) + ZnCl 2 (aq) Balancing equations involves placing coefficients that act as multipliers in front of a substance's formula. 2 Cl (aq) + Zn (s) 2 (g) + ZnCl 2 (aq) This shows that 2 moles of Cl are required to react with 1 mole of Zn.

8 Visualizing a Chemical Reaction 2 Na + Cl 2 2 NaCl 10 mole Na 5 mole Cl 2 10? mole NaCl

9 Visualizing a Chemical Reaction 2 Na + Cl 2 2 NaCl

10 Tips for Balancing Equation 2 Cl vs Cl 2 2 Cl means that there are TWO ATOMS of chlorine. Cl 2 means that there is one molecule of diatomic chlorine. Diatomic molecules (Br 2, I 2, N 2, Cl 2, 2, O 2, F 2 ) exist whenever these elements are not in a compound with another element.

11 Tips for Balancing Equation NEVER CANGE TE CEMICAL FORMULA!!! You can ONLY write coefficients to balance! 3PO 4 COEFFICIENT CEMICAL FORMULA

12 Separation of NaCl In NaCl, there is one Cl-1 ion (since Na is charged +1), but if that chlorine is separated from that compound: NaCl Na + Cl Then the Cl s thus formed will pair up diatomically, which throws off the balancing: NaCl Na + Cl 2

13 Ex.1: carbon reacts with oxygen gas to produce carbon dioxide: C O C + O 2 CO already balanced- 1: 1: 1 Ex.2: hydrogen gas reacts with oxygen gas to produce water: O balanced ratio- 2: 1: O O 2x 2=4 2x 2=4 2 2x 1=2

14 Balance the following equations ZnS + O 2 ZnO + SO 2 2ZnS + 3O 2 2ZnO + 2SO 2 Br 2 + FeI 3 I 2 + FeBr 3 <Even and Odd rule> Start off by putting an even number on the elements that are odd. 3Br 2 + 2FeI 3 3I 2 + 2FeBr 3

15 1. NaClO 2 3 NaCl 2 + O Fe 3 O Fe O Sample Problems: (Fe Single element) 1. ydrogen + oxygen water O O 2. Zinc + hydrochloric acid zinc chloride + hydrogen Zn + 2Cl ZnCl Copper + silver nitrate cupric nitrate + silver Cu + 2AgNO 3 Cu(NO 3 ) 2 + 2Ag (Keep NO 3 together) 4. Ferric hydroxide iron (III) oxide + water 2 Fe(O) 3 Fe 2 O O (O in multiple comp)

16 Click Below for the Video Lectures Conservation of Atoms

17 5. Ethane (C 2 6 ) + oxygen carbon dioxide + water 2 C O 2 4 CO O 6. Calcium + water calcium hydroxide + hydrogen Ca O Ca(O) Potassium + sulfuric acid potassium sulfate + hydrogen 2 K + 2 SO 4 K 2 SO Calcium nitrate + aluminum sulfite calcium sulfite + aluminum nitrate 3 Ca(NO 3 ) 2 + Al 2 (SO 3 ) 3 3 CaSO Al(NO 3 ) 3 9. Phosphoric acid is formed when crystalline diphosphorus pentoxide is dissolved in water. P 2 O O 2 3 PO 4

18 Reaction Types

19 Combustion occur when a compound or element react with oxygen to release energy and produce an oxide C O 2 3CO O C C C O O + O O + O O O O O O General Form: C X Y + O 2 CO O O O O C C C O O O + O O O O

20 Real World Application - COMBUSTION The burning of coal, a type of fossil fuel, is one of the most common real world applications of combustion to produce heat and energy. Combustion of coal, petroleum, hydrogen, biomass, etc. generates the largest amount of electricity worldwide. In the U.S., energy from coal is the major source (46.5%) of electricity production from June 2008 to June As a common combustion product, CO 2 is critical for global warming. Combustion of coal emits by far the greatest amount of CO 2 for the same amount of energy comparing to other types of energy sources. Other sources of energy include nuclear energy, renewable energy such as wind energy and solar energy, and so on, but they have constrains such as safety and cost. Although it might take decades to improve energy production technologies, they should be developed to provide more environmentally friendly and reliable energy sources for the future.

21 Synthesis Reaction Direct combination reaction Two elements combine to form a compound 2 Na + Cl 2 2 NaCl Na Na Cl Cl General form: A + B AB

22 Formation of a solid: AgCl AgNO 3 (aq) + KCl(aq) KNO 3 (aq) + AgCl(s)

23 Real World Application - SYNTESIS In chemical industry, the famous reaction of hydrogen gas and chlorine gas is applied in making hydrochloric acid. 2 + Cl 2 2Cl The rusting of iron can also be categorized as combination reaction. It is actually a very complicated reaction of iron, oxygen and water forming iron rust. Burning of coal : C + O 2 CO 2 Discharging of a battery is usually a combination reaction. For example, oxyhydrogen fuel cell: O O

24 Decomposition Reaction Reverse of synthesis a compound decomposes into its original elements 2 2 O O 2 O O + General form: AB A + B

25 Be careful! DO NOT split the formula and rewrite. MUST check the diatomic molecule!!! 2 2 O 2 + WRONG! O DIATOMIC MOLECULE!!!!!!!!!!! 2 + O 2 CORRECT!

26 Real World Application - DECOMPOSITION Decomposition reactions are used when heating CaCO 3 to make carbon dioxide. This practice is widely used in today's chemical industry. In the chemistry industry, decomposition reactions are applied to make high-purity hydrogen by electrolyzing water. When nitroglycerin, a primary ingredient in explosives, detonates, it rapidly decomposes to small gaseous molecules, such as carbon dioxide and water.

27 Single Replacement Reaction replace one element from a compound with another element CuCl 2 + Zn ZnCl + Cu 2 Cl Cu Cl + Zn Cl Zn Cl + Cu General form: A + BC B + AC where A is a metal, or A + BC C + BA where A is a non-metal

28 Be careful! DO NOT split the formula and rewrite. MUST check the ion and charges!!! Zn + NO 3 Charges are not +2-1 balanced! Diatomic Molecule WRONG! ZnNO 3 + Zn(NO 3 ) CORRECT!

29 Single Replacement Reaction Practice +3 Al + Ag 2 CO 3 Al 2 (CO 3 ) 3 + Ag Label the charges above each ion 2. Check the activity series 3. Write the product by balancing the charges 4. Balance the reaction ABOVE CAN REPLACE BELOW

30 Predict if these reactions will occur 3 Mg + 2 AlCl 3 2 Al + 3 MgCl 2 Can magnesium replace aluminum? Activity Series YES, magnesium is more reactive than aluminum. Al + MgCl 2 Can aluminum replace magnesium? Activity Series No reaction NO, aluminum is less reactive than magnesium. Therefore, no reaction will occur. MgCl 2 + Al No reaction Order of reactants DOES NOT determine how they react. The question we must ask is can the single element replace its counterpart? metal replaces metal or nonmetal replaces nonmetal.

31 Real World Application SINGLE REPLACEMENT In the steel industry, coke (a kind of coal) is used to replace iron out of ferric oxide. Another example is the Statue of Liberty, which has copper on the outside and iron as inner support. As time goes by, copper starts to react with air and form a verdigris coat; meanwhile, a single replacement reaction between iron and verdigris takes place so that verdigris on the outside is replaced back to copper but the iron support is oxidized and rusted. As a result, the entire inner support of the Statue of Liberty had to be replaced in the 1980s.

32 Double Displacement Reaction Two solutions react to form a precipitate (solid) and another solution. MgO + CaS MgS + CaO Mg O + Ca S Mg S + Ca O General Form: AB + CD AD + CB

33 Be careful! DO NOT split the formula and rewrite. MUST check the ion and charges!!! K 2 CrO 4 + 2AgNO WRONG! KNO 3 + AgCrO 4 Charges are not balanced! KNO 3 + Ag 2 CrO 4 CORRECT!

34 Double replacement reactions Precipitate Insoluble ions remain together. This is because the attractions between the ions are too strong for water molecules to tear apart. The ions come together and form crystals, which make the solution cloudy. The crystals are pulled to the bottom of the solution by gravity, forming a PRECIPITATE. K 2 CrO 4 + 2AgNO 3 Ag 2 CrO 4 + 2KNO 3

35 Solubility Rules Solubility rules can used to determine if a reaction will occur in a double displacement reaction. If both the products are soluble (form ions in solution), then no reaction has occurred.

36 Double Displacement Reaction 3CoCl 2(aq) + 2Na 3 PO 4(aq) Co 3 (PO 4 ) 2(s) + 6NaCl (aq) A reaction will occur only if the following will be produced 1)Gas 2)Solid precipitate Will this reaction occur? Precipitate Solubility table

37 Verifying Solubility Use your solubility chart to verity if the compound is soluble in water? a) MgCO 3 b) AgNO 3 c) MgCl 2 d) Na 3 PO 4 e) KO Insoluble Soluble Soluble Soluble Soluble

38 Double Replacement Reaction Practice Na 3 PO 4 (aq) + Mg(NO 3 ) 2 (aq) NaNO 3 + Mg 3 (PO 4 ) NaNO 3 (aq) + Mg 3 (PO 4 ) 2(s) 1. Label the charges above each ion 2. Write the product by balancing the charges 3. Check solubility using the rules 4. Label the correct state 5. Balance the reaction INSOLUBLE

39 Real World Application DOUBLE REPLACEMENT Soap was synthesized by the Egyptians, Romans, and Chinese using potassium hydroxide (KO). Each ancient civilization used unique procedures to synthesize KO. The ancient Chinese made KO using a doublereplacement reaction. Ancient Chinese people heated seashells and then mixed them with plant ash in water. (From unknown writer, Kao Gong Ji, ancient Chinese technology cyclopedia, as early as around 732 BCE)

40 Checking for understanding Complete the chart Type of reaction 1. General Form Example

41 Oxidation vs. Reduction driven by the loss of electrons (oxidation) and the gain of electrons (reduction).

42 Oxidation-Reduction Reaction Oxidation is loss of electrons. Reduction is gain of electrons. There is a very easy way to do this. As long as you remember that you are talking about electron transfer:

43 Neutralization occur when an acid (most compounds starting with ) and a base (most compounds ending in O) react to form a salt and water. Acid + Base Salt + Water Cl - O Na + Cl Na + O General Form: X + MO MX + 2 O where X and M are elements

44 Checking for understanding Explain in exactly 10 words each process. Your sentences do have to make sense: Oxidation Reduction Neutralization

45 Click Below for the Video Lectures Molecular, Ionic and Net Ionic Equations Synthesis, Decomposition Reactions Neutralization Reaction Redox Reaction