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Semester 1 Chemistry Review

Semester 1 Chemistry Review. DAY 2. Formula Weight. Find the formula weight of aluminum sulfate. Al 2 (SO 4 ) 3 Al - 2 x 26.98 = 53.96 S - 3 x 32.06 = 96.18 O - 12 x 16.00 = 192.00 + TOTAL 342.14 amu. Percent Composition.

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Semester 1 Chemistry Review

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  1. Semester 1 Chemistry Review DAY 2

  2. Formula Weight Find the formula weight of aluminum sulfate. • Al2(SO4)3 • Al - 2 x 26.98 = 53.96 • S - 3 x 32.06 = 96.18 • O - 12 x 16.00 = 192.00 + • TOTAL 342.14 amu

  3. Percent Composition • What is the percent composition of Aluminum, Sulfur, and Oxygen in Aluminum Sulfate? • Al - 2 x 26.98 = 53.96 / 342.14 x 100 • S - 3 x 32.06 = 96.18 / 342.14 x 100 • O - 12 x 16.00 = 192.00 / 342.14 x 100 • TOTAL 342.14 amu

  4. Answers Al2(SO4)3 is: 15.77 % Aluminum 28.11 % Sulfur 56.12 % Oxygen

  5. Mole Conversions • A mole is 6.02 x 1023 of anything. • There are 6.02 x 1023 amus in 1 gram. • 53.2 grams of aluminum sulfate is how many moles?

  6. Grams to Moles • 7.2 moles of Aluminum Sulfate is how many grams.

  7. Empirical vs. Molecular Formulas • Empirical Formulas are formulas whose subscripts are in their lowest terms. • Examples: Anything Ionic - Na2SO4 or CO2 or CH2O

  8. Molecular Formula • For ionic compounds, their molecular formula is the same as their empirical formula. • Some covalent molecules have molecular formulas that can be reduced to empirical formulas. • Examples - C6H12O6 or N2O4

  9. O - 47.04% Ca - 29.40% S - 23.56% = 2.94 = .7335 = .7349 O-4 Ca-1 S-1 Answer : CaSO4 What is the empirical formula for a compound made up of:

  10. Chemical Reactions Equations show: • 1. the reactants which enter into a reaction. • 2. the products which are formed by the reaction. • 3. the amounts of each substance used and each substance produced.

  11. Two important principles to remember: • Every chemical compound has a formula which cannot be altered. • A chemical reaction must account for every atom that is used. This is an application of the Law of Conservation of Matter which states that in a chemical reaction atoms are neither created nor destroyed.

  12. Some things to remember about writing equations: • The diatomic elements when they stand alone are always written: • H2, N2, O2, F2, Cl2, Br2, I2 • Before beginning to balance an equation, check each formula to see that it is correct. NEVER change a formula during the balancing of an equation.

  13. More Things to Remember: • Balancing is done by placing coefficients in front of the formulas to insure the same number of atoms of each element on both sides of the arrow. • The sign, → , means "yields" and shows the direction of the action.

  14. Types of Reactions • Composition • Decomposition • Replacement • Ionic (Double Replacement) • Combustion

  15. Composition Reaction • * two or more elements or compounds may combine to form a more complex compound. • * Basic form: A + X → AX • 2Mg + O2 → 2MgO

  16. Decomposition: • * A single compound breaks down into its component parts or simpler compounds. • * Basic form: AX → A + X

  17. 4 Types of Decomposition RXNS • 2 element decomposition • 2HgO → 2Hg + O2 • Metallic chlorates, • decompose into • metallic chlorides and oxygen. • 2KClO3 → 2KCl + 3O2

  18. Metallic carbonates, when heated, form metallic oxides and CO2. • CaCO3 → CaO + CO2 • Most metallic hydroxides, when heated, decompose into metallic oxides and water. • Ca(OH)2 → CaO + H2O

  19. (Single) Replacement • Replacement of a metal in a compound by a more active metal. • Fe + CuSO4 →FeSO4 + Cu • Replacement of nonmetals by more active nonmetals. • Cl2 + 2NaBr →2NaCl + Br2

  20. Ionic (Double Replacement) • NaCl + AgNO3 → • NaNO3 + AgCl • HCl + NaOH → • NaCl + H2O

  21. Combustion • Hydrocarbon + Oxygen • (CxHy) + O2 → CO2 + H2O • (CxHy) + O2 → CO + H2O

  22. Grams / Moles / Atoms • Grams A Moles A Atoms A • Grams B Moles B Atoms B

  23. Limiting Reagent Problems • 52.0g of hydrochloric acid react with 63.2 g of zinc. • What is the limiting reagent? • How much product is formed? • How much excess remains?

  24. 2HCl + Zn ---> ZnCl2 + H2 • 52.0g HCl • 63.2g Zn • 52.0g HCl

  25. 52.0g HCl 63.2g Zn 52.0g HCl = 1.44 g H2 = 1.95 g H2 = 97.2 g ZnCl2 2HCl + Zn ---> ZnCl2 + H2

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