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Catalyst

Catalyst. 1. To fill up a cup with water, let’s say you need 5 billion molecules of water. How many atoms of hydrogen is that? How many atoms of oxygen? 2. When you heat up food in the microwave, how do you know how long to set it for?. What is balanced in a chemical equation?.

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Catalyst

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  1. Catalyst 1. To fill up a cup with water, let’s say you need 5 billion molecules of water. How many atoms of hydrogen is that? How many atoms of oxygen? 2. When you heat up food in the microwave, how do you know how long to set it for?

  2. What is balanced in a chemical equation? Three things are balanced in a chemical equation: 1. Atoms 2. Mass 3. Charge

  3. Balancing Chemical Equations Atoms must be conserved!

  4. For now, you will only be concerned with balancing atoms. Remember, the number of atoms of each element on the reactants side must equal the number of atoms of each element on the products side!

  5. Counting Atoms • How many atoms of each element are in the following molecules? 1. H2SO4 2. CaOH2 3. NaCl 4. (NH3)3PO4 5. 3H2O

  6. Answers • 1. 2 hydrogen, 1 sulfur, 4 oxygen • 2. 1 calcium, 1 oxygen, 2 hydrogen • 3. 1 sodium, 1 chlorine • 4. 3 nitrogen, 9 hydrogen, 1 phosphorus, 4 oxygen • 5. 6 hydrogen, 3 oxygen

  7. Is this equation balanced? • NaCl + H2O  NaOH + Cl2 • left side has 1Na, 1Cl, 2H, and 1O • right side has 1Na, 1O, 1H, and 2Cl • NO! It is not balanced!

  8. Is this equation balanced? • HCl + NaOH NaCl+ H2O • left side has 2H, 1Cl, 1Na, and 1O • right side has 1Na, 1Cl, 2H, and 1O • Yes! It is balanced!

  9. Is this equation balanced? • Ca + H2O Ca(OH)2 + H2 • left side has 1Ca, 2H, 1O • right side has 1Ca, 2O, 4H • No! It is not balanced! • How can we make it balance?

  10. Ca + H2O  Ca(OH)2 + H2 • We need more H’s, but we can’t add just the H atom, we have to add the entire molecule the H is attached to: Ca + H2O Ca(OH)2 + H2 H2O Count the boxes. These are the coefficients: 1 Ca + 2 H2O  1 Ca(OH)2 + 1 H2

  11. 1 Ca + 2 H2O  1 Ca(OH)2 + 1 H2 • Just like in math, this equation may be written in a simpler way: • Ca + 2 H2O Ca(OH)2 + H2

  12. The End • Let’s practice!

  13. 1. __H3PO4 + __KOH  __K3PO4 + _H2O 2. __K + __B2O3 __K2O + __B 3. __Na + __NaNO3 __Na2O + __N2 4. __Na + __O2 __Na2O 5. __H3PO4 + __Mg(OH)­2  __Mg3(PO4)2 + __H2O 6. __NaOH + __H2CO3  __Na2CO3 + __H2O 7. __Al(OH)3 + __H2CO3  __Al2(CO3)3 + __H2O 8. __Rb + __NO3 __Rb2O + __N2

  14. Percent Composition If the formula of a compound is known, it is a fairly straightforward task to determine the percent composition of each element in the compound. For example, suppose you want to calculate the percentage hydrogen and oxygen in water, H2O. First calculate the molecular mass of water: 1 mol H2O = 2 mol H + 1 mol O Substituting the masses involved: 1 mol H2O = 2 (1.0079 g/mol) + 16.00 g/mol = 18.0158 g/mol

  15. percentage hydrogen = [mass H/mass H2O] × 100 = [2(1.0079 g/mol)/18.0158 g/mol] × 100 = 11.19% H • percentage oxygen = [mass O/mass H2O] × 100= [16.00 g/mol/18.0158 g/mol] × 100 = 88.81% O • As a good check, add the percentages together. They should equal to 100% or be very close.

  16. Determine the mass percent of each of the elements in C6H12O6

  17. ANSWER • Formula mass= 180.158 amu • %C =(6C atoms)(12.011 amu/atom)/(180.158 amu) x 100% = 40.002% • %H =(12H atoms)(1.008 amu/atom)/(180.158 amu) x 100% = 6.714% • %O =(6O atoms)(15.9994 amu/atom)/(180.158 amu) x 100% = 53.2846% • Total =100 001 . %

  18. Empirical Formula The empirical formula tells us what elements are present in the compound and the simplest whole-number ratio of elements. The data may be in terms of percentage, or mass, or even moles. But the procedure is still the same: convert each to moles, divide each by the smallest number, then use an appropriate multiplier if needed.

  19. Molecular (Actual) Formula If the actual molecular mass is known, dividing the molecular mass by the empirical formula mass gives an integer (rounded if needed) that is used to multiply each of the subscripts in the empirical formula. This gives the molecular (actual) formula, which tells which elements are in the compound and the actual number of each.

  20. Example For example, a sample of a gas was analyzed and found to contain 2.34 g of nitrogen and 5.34 g of oxygen. The molar mass of the gas was determined to be about 90 g/mol.

  21. Answer ( 2.34g N)x(1mol N/14.0 g N) = 0 .167 N (1.67/1.67) = 1 N (5.34 g O) (1 mol O/ 16.0 g O) = 0.334 mol O (0.334 / 0.167) = 2 O Therefore Empirical Formula = NO2

  22. Answer The molecular formula may be determined by dividing the actual molar mass of the compound by the empirical molar mass. In this case the empirical molar mass is 46 g/mol. Thus (90g/mol / 46g/mol) = 1.96 which, to one significant figure, is 2. Therefore, the molecular formula is twice the empirical formula—N2O4.

  23. PRACTICE PROBLEMS 1.) What is the percent composition of N2O4? 2.) What is the empirical formula of methyl acetate 97.28 g carbon, 16.22 g hydrogen, and 86.40 g oxygen. 3.) A compound containing barium, carbon, and oxygen has the following percent composition: 69.58g Ba, 6.09g C, 24.32g O. What is the empirical formula for this compound? 4.) What is the empirical and molecular formula of Vitamin D3 if it contains 84.31% C, 11.53% H, and 4.16% O, with a molar mass of 384 g/mol?

  24. ANSWERS 1.) 30.4% N and 69.6% O 2.) C3H6O2 3.)BaCO4 4.)C27H44O (both)

  25. NOMENCLATURE The flowchart gives explicit instructions on how to name compounds Work backwards on the flowchart to determine the formula Change ternarny to tertiary

  26. For each of the following questions, determine whether the compound is ionic or covalent and name it appropriately. • 1) HClO4 • 2) P2O5 • 3) NH3 • 4) FeSO4 • 5) SiO2 • 6) GaCl3 • 7) CoBr2 • 8) B2H4 • 9) CO • 10) HClO

  27. For each of the following questions, determine whether the compound is ionic, covalent or acidic and write the appropriate formula for it. • 11) dinitrogen trioxide • 12) nitrous acid • 13) hydroiodic acid • 14) lithium acetate • 15) phosphorus trifluoride • 16) vanadium (V) oxide • 17) aluminum hydroxide • 18) Arsenous acid • 19) silicon tetrafluoride • 20) silver phosphate

  28. For each of the following questions, determine whether the compound is ionic or covalent and name it appropriately. • 1) BBr3 • 2) CaSO4 • 3) HBr • 4) Cr(CO3)3 • 5) Ag3P • 6) H2SO3 • 7) VO2 • 8) PbS • 9) CH4 • 10) N2O3

  29. Write the formulas of the following chemical compounds: • 11) tetraphosphorustriselenide • 12) potassium acetate • 13) iron (II) phosphide • 14) disiliconhexabromide • 15) titanium (IV) nitrate • 16) hydrophosphoric acid • 17) copper (I) phosphate • 18) gallium sulfide • 19) tetrasulfurdinitride • 20) bromic acid

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