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Chapter 3A

Chapter 3A. chemical bonds - what holds compounds together -bonds can be ionic or molecular/covalent chemical formula - shows the kinds and number of each element in a compound ex- H 2 O CO 2 H 3 PO 4 structural formula - uses lines to show bonds ex- O O ═ C ═ O H H.

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Chapter 3A

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  1. Chapter 3A chemical bonds- what holds compounds together -bonds can be ionic or molecular/covalent chemical formula- shows the kinds and number of each element in a compound ex- H2O CO2 H3PO4 structural formula- uses lines to show bonds ex- O O ═ C ═ O H H

  2. empirical formula- gives the relative number of atoms of each element in a compound -lowest whole number ratio molecular formula- gives the actual number of atoms of each element in a compound ex- hydrogen peroxide H2O2 emp. = HO (H and O in a 1:1 ratio) mol. = H2O2 page 87 Ex 3.1 and FP 3.1

  3. atomic elements- exist in nature as single atoms -almost all the elements can exist as atoms -called monatomic molecular elements- cannot exist in nature as one atom, cannot exist alone -exist as molecules H O N Cℓ Br I F -called diatomic

  4. Ions- particles with a charge (+ or -), they have either lost or gained electrons -in ions # of p+≠ # of e- cation -ion with a positive charge -loses electrons -metallic elements lose electrons -look at Group # to get the charge for Groups 1A to 3A

  5. ex- sodium Na1+ or Na+1 or Na+ aluminum Aℓ3+ -sodium lost 1e-, aluminum lost 3 e- **Most cations of the transition metals have more than one charge -these will need to be given to you ex- Pb4+ lost 4e- -a few have only one charge Ag1+ Zn2+ Cd2+ -silver lost 1e-, zinc and cadmium each lost 2e-

  6. anions -ion with a negative charge -gains electrons -non-metallic elements gain electrons -look at Group # - 8 to get the charge ex- chlorine Cℓ1- arsenic As3- -chlorine gained 1e- -arsenic gained 3e- *Group 4 elements do not generally form ions, Group 8 do not b/c they are inert

  7. Naming Ions Cations -name is the same as the element with the word ion -back to examples sodium ion aluminum ion lead (IV) ion Anions -drop ending and add –ide and the word ion -back to examples -chloride ion -arsenide ion

  8. Try these!! -name the ion/tell if it is a cation or anion -tell the charge on the ion -tell how e- the ion has lost or gained Sr I Ca K P B S polyatomic ions- made up or two or more atoms that carry a charge *most names end in –ite or –ate

  9. Ionic Compounds -compounds composed of cations and anions -made up of a metal (cation) and a non-metal (anion) -usually solid crystals at room temp -have high melting points -are electrically neutral because # of p+ = # of e- ex- NaCℓ KI Ca3N2 formula unit- chemical formula for an ionic compound

  10. Molecular Compounds -made up of two or more non-metals Binary Molecular Compounds -made up of two non-metals Ex- CO, CO2, CCℓ4 -to name molecular compounds you use prefixes

  11. Prefix# (subscript) mono- 1 di- 2 tri- 3 tetra- 4 penta- 5 hexa- 6 hepta- 7 octa- 8 nona- 9 deca- 10

  12. Naming Molecular Compounds -look at subscript of each element and give each element a prefix -if first element has a 1 as the subscript, then it does not get a prefix (omit mono-) -second element gets prefix and ends in –ide -if element begins with a vowel, drop the vowel at the end of a prefix **when writing formulas for molecular compounds you DO NOT reduce subscripts

  13. Try these!! carbon monoxidecarbon tetrachloride sulfur trioxide tetriodinenonoxide phosphorus pentafluoride N2O PCℓ3 SF6 OF2 CℓO8 NF3 S2Cℓ2 N2O4

  14. Acids -acids are compounds dissolved in water -will have (aq) after the formula which means aqueous or dissolved in water -always begin with hydrogen (H) Ex- HCℓ H2SO4 H3PO3 Naming Acids -you must look at what follows the hydrogen

  15. -if it is a single element (ends in –ide), then you use prefix hydro-, root of the element, -ic ending and the word acid ex- HCℓ hydrochloric acid -if what follows hydrogen ends in –ite, you just add –ous ending to root of the polyatomic ion and add acid ex- H3PO3 phosphorous acid

  16. -if what follows hydrogen ends in –ate, you just add –ic ending to root of the polyatomic ion and add acid ex- H2SO4 sulfuric acid Try these!! HI H2S H2CO3 H2SO3 HNO2 HCℓO3

  17. Chemical Equations reactants  products reactant- starting substance in a chemical reaction product- substance formed in a chemical reaction • = yields, gives you, produces, goes to **Law of Conservation of Mass holds true here mass of reactants = mass of products

  18. -the states of matter can be indicated after the substance (s)=solid (ℓ)=liquid (g)=gas (aq)=aqueous = reversible reaction catalyst- substance that speeds up the rate of a reaction without being used up in the reaction **written above the arrow ex- Pt ∆ = heat applied

  19. **Remember H O N Cℓ Br I F skeleton equation- chemical equation that is not balanced ex- Write a skeleton for the following reaction: solid iron reacts with oxygen to form solid iron (III) oxide Fe + O2 Fe2O3

  20. Try these: 1) solid sodium hydrogen carbonate reacts with hydrochloric acid to produce aqueous sodium chloride, water and carbon dioxide • solid sulfur burns in oxygen to form sulfur dioxide • solid potassium chlorate forms oxygen and solid potassium chloride in the presence of catalyst manganese(II) oxide

  21. Answers 1)NaHCO3(s) + HCℓ(aq)  NaCℓ(aq) + H2O (ℓ) + CO2(g) • S(s) + O2(g)  SO2(g) 3) KCℓO3(s) MnOO2(g) + KCℓ(s)

  22. Balancing Equations -each side of the equation (reactants and products) must have the same # of each element -some may already be balanced -must be lowest whole # ratio -balance by putting coefficients in front of compounds

  23. Types of Chemical Reactions • Combination/Synthesis Reaction -two or more substances combine to form a single substance reactants- two elements or two compounds products- always a compound ex- 2K + Cℓ2 2KCℓ ex- SO2 + H2O  H2SO3

  24. Try these!! Don’t forget to balance!! a) aluminum + oxygen b) copper + sulfur (two possible reactions) c) beryllium + oxygen d) strontium + iodine e) magnesium + nitrogen a) 4Aℓ + 3O2 2Aℓ2O3 b) 2Cu + S  Cu2S or Cu + S  CuS c) 2Be + O2  2BeO d) Sr + I2 SrI2 e) 3Mg + N2 Mg3N2

  25. Decomposition Reaction -one compound breaks down or decomposes into two simpler compounds -the reverse of synthesis ex- 2H2O  2H2 + O2 Try these!! a) lead(IV) oxide  b) hydrogen iodide  c) hydrogen bromide  d) sodium chloride 

  26. PbO2 Pb + O2 • 2HI  H2 + I2 • 2HBr  H2 + Br2 • 2NaCℓ  2Na + Cℓ2 • Single-Replacement Reactions -one element replaces a second element in a compound ex- 2K + CaO  K2O + Ca -whether one metal will replace another metal is determined by reactivity of the metal

  27. activity series of metals- lists metals in order of decreasing reactivity

  28. ex- Mg + Zn(NO3)2 *is Mg above Zn on the reactivity series? Mg + Zn(NO3)2 Mg(NO3)2 + Zn ex- Mg + Ag2SO4  Mg + Ag2SO4  MgSO4 + 2Ag ex- Mg + LiNO3  -lithium is above magnesium Mg + LiNO3  no reaction

  29. -Halogens can replace each other in single-replacement reactions -Reactivity decreases as you go down the halogen group Try These!! a) zinc + hydrogen sulfate  b) chlorine + sodium bromide  c) zinc + sodium nitrate  d) iron(II) + lead(II) nitrate  e) chlorine + sodium iodide 

  30. a) Zn + H2SO4 H2 + ZnSO4 b) Cℓ2 + 2NaBr  Br2 + 2NaCℓ c) Zn + NaNO3  no reaction d) Fe + Pb(NO3)2  Pb + Fe(NO3)2 e) Cℓ2 + 2NaI  I2 + 2NaCℓ

  31. Double-Replacement Reactions -involve an exchange of cations between two reacting compounds ex- BaCℓ2 + K2CO3 BaCO3 + 2KCℓ ex- FeS + 2HCℓ  H2S + FeCℓ2 Try These!! • sodium hydroxide + iron(III) nitrate  • barium nitrate + hydrogen phosphate  • potassium hydroxide+hydrogen phosphate  • hydrogen sulfate + aluminum hydroxide 

  32. Answers • 3NaOH + Fe(NO3) 3 3NaNO3 + Fe(OH)3 • 3Ba(NO3) 2 + 2H3PO 4Ba3(PO4) 2 + 6HNO3 • 3KOH + H3PO4  K3PO4 + 3H2O • 3H2SO4 + 2Aℓ(OH)3 Aℓ2(SO4)3 + 6H2O

  33. Combustion Reaction -hydrocarbon combined with oxygen to produce carbon dioxide and water ex- C6H6 + O2 CO2 + H2O -to balance: CxHy + O2 CO2 + H2O (x+y/4) (x) (y/2) C6H6 + 7.5O2 6CO2 + 3H2O -multiply by 2 to get whole number ratio 2C6H6 + 15O2 12CO2 + 6H2O

  34. Try These!! • C14H26 + O2 CO2 + H2O • C8H12 + O2 CO2 + H2O Answers! • 2C14H26 + 41O2 28CO2 + 26H2O • C8H12 + 11O2 8CO2 + 6H2O

  35. Summary of Reactions • Combination/Synthesis R + S  RS • Decomposition Reaction RS  R + S • Single-Replacement Reaction T + RS  R + TS • Double-Replacement Reaction RS + TU  RU + TS • Combustion Reaction CxHy + O2 CO2 + H2O

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