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

Balancing Chemical Equations Atoms must be conserved!

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! 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!

Counting Atoms How many atoms of each element are in the following molecules?How many atoms of each element are in the following molecules? 1. H 2 SO 4 2. CaOH 2 3. NaCl 4. (NH 3 ) 3 PO H 2 O

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

Is this equation balanced? NaCl + H 2 O  NaOH + Cl 2 NaCl + H 2 O  NaOH + Cl 2 left side has 1Na, 1Cl, 2H, and 1Oleft side has 1Na, 1Cl, 2H, and 1O right side has 1Na, 1O, 1H, and 2Clright side has 1Na, 1O, 1H, and 2Cl NO! It is not balanced!NO! It is not balanced!

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

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

Ca + H 2 O  Ca(OH) 2 + H 2 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: 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 + H 2 O  Ca(OH) 2 + H 2 H2O H2O H2O H2O Count the boxes. These are the coefficients: 1 Ca + 2 H 2 O  1 Ca(OH) H 2 1 Ca + 2 H 2 O  1 Ca(OH) H 2

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

The End Let’s practice! Let’s practice!

1. __H 3 PO 4 + __KOH  __K 3 PO 4 + _H 2 O 2. __K + __B 2 O 3  __K 2 O + __B 3. __Na + __NaNO 3  __Na 2 O + __N 2 4. __Na + __O 2  __Na 2 O 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 + __NO 3  __Rb 2 O + __N 2

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: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 O1 mol H2O = 2 mol H + 1 mol O Substituting the masses involved:Substituting the masses involved: 1 mol H2O = 2 ( g/mol) g/mol = g/mol1 mol H2O = 2 ( g/mol) g/mol = g/mol

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

Determine the mass percent of each of the elements in C6H12O6Determine the mass percent of each of the elements in C6H12O6

ANSWERANSWER –Formula mass= amu –%C =(6C atoms)( amu/atom)/( amu) x 100% = % –%H =(12H atoms)(1.008 amu/atom)/( amu) x 100% = 6.714% –%O =(6O atoms)( amu/atom)/( amu) x 100% = % –Total = %

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.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.

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.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.

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.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.

Answer ( 2.34g N)x(1mol N/14.0 g N) = N( 2.34g N)x(1mol N/14.0 g N) = N (1.67/1.67) = 1 N(1.67/1.67) = 1 N (5.34 g O) (1 mol O/ 16.0 g O) = mol O(5.34 g O) (1 mol O/ 16.0 g O) = mol O (0.334 / 0.167) = 2 O(0.334 / 0.167) = 2 O Therefore Empirical Formula = NO2Therefore Empirical Formula = NO2

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.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.Thus (90g/mol / 46g/mol) = 1.96 which, to one significant figure, is 2. Therefore, the molecular formula is twice the empirical formula—N2O4.

PRACTICE PROBLEMS 1.) What is the percent composition of N2O4? 2.) What is the empirical formula of methyl acetate g carbon, g hydrogen, and 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 D 3 if it contains 84.31% C, 11.53% H, and 4.16% O, with a molar mass of 384 g/mol?

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

NOMENCLATURE The flowchart gives explicit instructions on how to name compoundsThe flowchart gives explicit instructions on how to name compounds Work backwards on the flowchart to determine the formulaWork backwards on the flowchart to determine the formula Change ternarny to tertiaryChange ternarny to tertiary

For each of the following questions, determine whether the compound is ionic or covalent and name it appropriately. 1) HClO41) HClO4 2) P2O52) P2O5 3) NH33) NH3 4) FeSO44) FeSO4 5) SiO25) SiO2 6) GaCl3 7) CoBr2 8) B2H4 9) CO 10) HClO

For each of the following questions, determine whether the compound is ionic, covalent or acidic and write the appropriate formula for it. 11) dinitrogen trioxide11) dinitrogen trioxide 12) nitrous acid12) nitrous acid 13) hydroiodic acid13) hydroiodic acid 14) lithium acetate14) lithium acetate 15) phosphorus trifluoride15) phosphorus trifluoride 16) vanadium (V) oxide 17) aluminum hydroxide 18) Arsenous acid 19) silicon tetrafluoride 20) silver phosphate

For each of the following questions, determine whether the compound is ionic or covalent and name it appropriately. 1) BBr31) BBr3 2) CaSO42) CaSO4 3) HBr3) HBr 4) Cr(CO3)34) Cr(CO3)3 5) Ag3P5) Ag3P 6) H2SO3 7) VO2 8) PbS 9) CH4 10) N2O3

Write the formulas of the following chemical compounds: 11) tetraphosphorus triselenide11) tetraphosphorus triselenide 12) potassium acetate12) potassium acetate 13) iron (II) phosphide13) iron (II) phosphide 14) disilicon hexabromide14) disilicon hexabromide 15) titanium (IV) nitrate15) titanium (IV) nitrate 16) hydrophosphoric acid 17) copper (I) phosphate 18) gallium sulfide 19) tetrasulfur dinitride 20) bromic acid