Conversions Balancing Equations Mr Ramos What are Conversions

Conversions & Balancing Equations Mr. Ramos

What are Conversions? �

Conversion Examples �

Chemistry Example � The gasoline in an automobile gas tank has a mass of 60. 0 kg and a density of 0. 752 g/cm 3. What is its volume in cm 3?

Where are the Units? � What is the mass of Hydrogen, Carbon, or Oxygen? ◦ Go to the periodic table and try to find the corresponding unit associated with the mass of these elements. � Hydrogen’s mass is 1. 01 what? � Carbon’s mass is 12. 01 what? � Oxygen’s mass is 16. 00 what? � Where are the UNITS?

Where are the Units? � The atomic mass unit (amu), or Dalton, is used to indicate the mass of atoms and molecules. ◦ Hydrogen has a mass of 1. 01 amu ◦ Carbon has a mass of 12. 01 amu ◦ Oxygen has a mass of 16. 00 amu � � If, however, we have a fixed amount of any element that equals 6. 022 x 1023, then the mass of that element is changed from amu to grams. 1 mole = 6. 022 x 1023 (Avogadro’s Number)

The Mole � The element hydrogen has a mass of 1. 01 amu. � The element carbon has a mass of 12. 01 amu. � The element oxygen has a mass of 16. 00 amu. ◦ However, 1 mole of hydrogen has a mass of 1. 01 grams. ◦ However, 1 mole of carbon has a mass of 12. 01 grams. ◦ However, 1 mole of oxygen has a mass of 16. 00 grams. � Do � 1 you notice the pattern? mole of anything contains 6. 022 x 1023 particles

The Mole: Avogadro’s # � 1 mole of M&M’s = 6. 022 x 1023 M&M’s ◦ That’s a lot of M&M’s (Yummy) � 1 mole of U. S. dollars = 6. 022 x 1023 U. S. dollars ◦ I would be rich! YES! � 1 mole of carbon = 6. 022 x 1023 carbon atoms = 12. 01 grams of carbon

Conversions Involving Moles � 6 CO 2 + 6 H 2 O + Sunlight C 6 H 12 O 6 + 6 O 2 � The formula above represents the photosynthesis equation. � How many grams of glucose are produced when 12 moles of carbon dioxide are consumed?

Solve by Converting � Sodium chloride, Na. Cl, forms by the following reaction between sodium and chlorine. ◦ 2 Na (s) + Cl 2 (g) 2 Na. Cl (s) � How many moles of Na. Cl result from the complete reaction of 3. 4 mol of Cl 2? Assume that there is more than enough Na.

Solve by Converting � Water is formed when hydrogen gas reacts explosively with oxygen as according to the following balanced equation. ◦ O 2 (g) + 2 H 2 (g) 2 H 2 O (g) � How many moles of H 2 O result from the complete reaction of 24. 6 mol of O 2? Assume that there is more than enough H 2.

Solve by Converting � How many moles of ammonia (NH 3) are produced when 0. 60 mol of nitrogen (N 2) reacts with Hydrogen (H 2)? ◦ N 2 (g) + 3 H 2 (g) 2 NH 3 (g)

Law of Conservation of Mass � For any closed system, mass cannot be created or destroyed. ◦ Mass can only be transferred. Reactants Products

Balanced Chemical Equations � Chemical � 6 CO 2 equations must always be balanced. + 6 H 2 O C 6 H 12 O 6 + 6 O 2 Carbon = 6 Oxygen = 18 Hydrogen = 12 Reactants Products

Writing Balanced Chemical Equations � 1. Write a skeletal equation by writing chemical formulas for each of the reactants and products. � Si. O 2 (s) + C (s) Si. C (s) + CO (g)

Writing Balanced Chemical Equations � Si. O 2 (s) + C (s) Si. C (s) + CO (g) � 2. If an element occurs in only one compound on both sides of the equation, balance it first. If there is more than one such element, balance metals before nonmetals. � Begin with Si: 1 Si atom ◦ Si is already balanced � Balance O next: 2 O atoms 1 O atom ◦ To balance O, put a 2 before CO (g) ◦ Si. O 2 (s) + C (s) Si. C (s) + 2 CO (g)

Writing Balanced Chemical Equations � Si. O 2 (s) + C (s) Si. C (s) + 2 CO (g) � 3. If an element occurs as a free element on either side of the chemical equation, balance it last. Always balance free elements by adjusting the coefficient on the free element. � Balance C: 1 C 3 C ◦ To balance C, put a 3 before C (s) ◦ Si. O 2 (s) + 3 C (s) Si. C (s) + 2 CO (g)

Writing Balanced Chemical Equations � Si. O 2 (s) + 3 C (s) Si. C (s) + 2 CO (g) � 4. If the balanced equation contains coefficient fractions, clear these by multiplying the entire equation by the appropriate factor. � This step is not necessary in this example.

Writing Balanced Chemical Equations � 5. Check to make certain the equation is balanced by summing the total number of each type of atom on both sides of the equation. � Si. O 2 (s) + 3 C (s) Si. C (s) + 2 CO (g) Silicon = 1 Oxygen = 2 Carbon = 3

Writing Balanced Chemical Equations: Solve � C 8 H 18 (l) + O 2 (g) CO 2 (g) + H 2 O (g)

Writing Balanced Chemical Equations: Solve � Fe (s) + 3 HCl (aq) Fe. Cl 3 (aq) + H 2 (g)