1 f. un. Al O 1 f. un. Al O 1 f. un. Al O 1 f. un. Al O 1 f. un. Al O 1 f. un. Al O. 5 ions

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1 CH 11 T36 COMPOUND CONVERSIONS & AVOGADRO S NUMBER 1 You have mastered this topic when you can: 1) create and use COMPOUND CONVERSION FACTORS. 2) state AVOGADRO S CONSTANT. COMPOUND CONVERSION FACTORS I) A compound s chemical formula tells us the different kinds of elements and the number of atoms of each different element it contains. e.g. The molecule CO 2 can be written as C 1 O 2 which contains 1 C atom and 2 atoms O The molecule H 2 S can be written as H 2 S 1, which contains 2 H atoms, 1 S atom, and 4 atoms O The ionic compound for Al 2 O 3 contains 2 Al 3+ ions and 3 ions O 2 The ionic compound for Sc 2 (S ) 3 can be written as Sc 2 (S 1 ) 3 which contains 2 Sc 3+ ions, 3 S 2 ions, 5 ions in total, 2 Sc atoms, 1 x 3 = 3 atoms S, 4 x 3 = 12 atoms O, and 17 atoms in total The ionic compound for Pb 3 (P ) 2 can be written as Pb 3 (P 1 ) 2 which contains 3 Pb 2+ ions, 2 P 3 ions, 5 ions in total, 3 Pb atoms, 1 x 2 = 2 P atoms, 4 x 2 = 8 atoms O, and 13 atoms in total A) COMPOUND CONVERSION FACTORS ARE CREATED DIRECTLY FROM THE FORMULA OF THE COMPOUND OR MOLECULE 1) Sample Problems 1: Write compound conversion factors for these compounds. a. The three compound conversion factors for the molecule N 2 are given here. NOTE: molec = molecule 2 atoms N 5 atoms O 7 atoms 1 molec N O 1 molec N O 1 molec N O b. The six compound conversion factors for the formula unit Al 2 O 3 are given here. NOTE: f. un. = Formula units 2 ions Al3+ 3 ions O2 5 ions 2 atoms Al 3 atoms atoms 1 f. un. Al O 1 f. un. Al O 1 f. un. Al O 1 f. un. Al O 1 f. un. Al O 1 f. un. Al O c. The seven compound conversion factors for Sc 2 (S ) 3 are given here. 2 ions Sc 3+ 1 f. un. Sc 2 S 12 atoms O 1 f. un. Sc 2 S 2 3 ions S 5 ions 2 atoms Sc 3 atoms S ( ) 1 f. un. Sc 3 2 ( S ) 1 f. un. Sc 3 2 ( S ) 1 f. un. Sc 3 2 ( S ) 1 f. un. Sc 3 2 ( S ) 3 17 atoms 1 f. un. Sc 2 ( SS ) 3 2) REMEMBER: In a compound conversion factor the formula of the compound or molecule ALWAYS has the 1. 3) Required Practice 1: Write all the compound conversion factors as possible for each of these compounds. 1. C 2 H 4 2. NiBr 3 3. KNO 3 4. Ba 3 (P ) 2 {Ans: See your teacher.} B) CONVERTING NUMBER OF MOLECULES OR FORMULA UNITS TO NUMBER OF ATOMS OR IONS 1) The compound conversion factors created from a compound s chemical formula are used to calculate the number of atoms or ions in a sample of the compound. a) Sample Problems 2 1. Calculate the number of nitrogen atoms in 19 N 2 molecules. 19 molec N 2 2 atoms N 1 molec N 2 = 38 atoms N

2 CH 11 T36 COMPOUND CONVERSIONS & AVOGADRO S NUMBER 2 2. Calculate the number of sulphate ions in 3 Ni 2 (S ) 3 formula units. 3 f. un. Ni 2 ( S ) 3 3 ions SO f. un. Ni 2 S = 9 ions S 2 3. How many oxygen atoms are in 5.5 x Ni 3 (P ) 2 formula units? f. un. Ni 3 P ( ) 2 8 atoms O 1 f. un. Ni 3 P ( ) 2 = atoms O b) Required Practice 2: Show all your work!! {Answers are on page 4.} 1. Calculate the number of nitrogen atoms in 49 N 2 O molecules. 2. Determine the number of NH 4 + ions in 3 (NH 4 ) 3 P formula units. 3. How many hydrogen atoms are in 5 formula units of (NH 4 ) 3 P? 4. How many oxygen atoms are in 4.7 x (NH 4 ) 3 P formula units? 5. How many nitrogen atoms are in 8.6 x formula units of (NH 4 ) 3 P? 6. Determine the number of atoms in x (NH 4 ) 3 P formula units. 7. Determine the number of ions in x formula units of (NH 4 ) 3 P. 8. Calculate the number of OH - ions in 5.6 x Ca(OH) 2 formula units. 9. Calculate the number of O atoms in 2.76 x formula units of Ca(OH) Calculate the number of atoms in x Ca(OH) 2 formula units. C) CONVERTING NUMBER OF ATOMS OR IONS TO NUMBER OF MOLECULES OR FORMULA UNITS 1) The compound conversion factors created from a compound s chemical formula are used to calculate the number of molecules or formula units created from a given number of atoms or ions. a) Sample Problems 3 1. Calculate the number of dinitrogen tetroxide molecules formed when 396 oxygen atoms react with excess nitrogen. 396 atoms O 1 molec N 2 4 atoms O = 99.0 molec N 2 2. How many Ni 3 (P ) 2 formula units can be created from x phosphate ions reacting with excess nickel? ions P 3 1 f. un. Ni 3 ( P ) 2 3 = f. un. Ni 2 ions PO 3 ( P ) 2 4 b) Required Practice 3: Show all your work!! {Answers are on page 4.} 1. Calculate the number of N 2 O molecules created from 68 nitrogen atoms reacting with excess oxygen NH 4 + ions react with excess phosphate ions. How how many (NH 4 ) 3 P formula units are created? 3. How many (NH 4 ) 3 P formula units will be produced from x hydrogen atoms? x oxygen atoms will produce how many (NH 4 ) 3 P formula units? 5. Determine the number molecules of hydrogen peroxide formed from x hydrogen atoms. AVOGADRO S CONSTANT I) AVOGADRO S CONSTANT is the calculated value x particles. Since this is a calculated value, its precision is limited and thus must be considered when determining significant digits in calculations. Use the rounded value of 6.02 x particles as Avogadro s constant. BECAUSE AVOGADRO S CONSTANT IS THE ROUNDED VALUE OF A CALCULATED VALUE IT HAS THREE SIGNIFICANT DIGITS.

3 CH 11 T36 COMPOUND CONVERSIONS & AVOGADRO S NUMBER 3 A) The MOLE, symbolized mol, is equal to 6.02 x particles of a substance. REMEMBER that particles can be atoms, ions, molecules or formula units. 1) AVOGADRO S CONVERSION FACTOR (Avogadro s cf) MEMORIZE IT!! Written as an equality 1 mol particles = particles Written as a conversion factor 1 mol Particles Particles 23 OR Particles 1 mol Particles a) i.e. 1 mole of calcium atoms contains 6.02 x atoms of calcium 1 mole of O 2- ions contains 6.02 x ions O 2 1 mole of Al 2 O 3 contains 6.02 x formula units of Al 2 O 3 1 mole of Ba(NO 3 ) 2 contains 6.02 x formula units of Ba(NO 3 ) 2 II) CALCULATIONS INVOLVING AVOGADRO S NUMBER AND THE MOLE A) Avogadro s conversion factor is used to convert number of moles to number of particles and vice versa. MEMORIZE THESE PATTERNS!! 1) Converting number of moles to number of molecules or formula units. # mol x Avogadro s cf = # of molecules or formula units 2) Converting number of molecules or formula units to number of moles. # of molecules or formula units x Avogadro s cf = # mol B) CONVERTING NUMBER OF MOLES TO NUMBER OF MOLECULES OR FORMULA UNITS # mol x Avogadro s cf = # of molecules or formula units 1) Sample Problems moles of N 2 is equal to how many molecules of N 2? # mol x Avogadro s cf = # of molecules 3.67 mol N molec N 2 1 mol N 2 = molec N 2 = molec N moles of Al(NO 3 ) 3 is equal to how many Al(NO 3 ) 3 formula units? # mol x Avogadro s cf = # of formula units 0.47 mol Al( NO 3 ) f. un. Al NO 3 1 mol Al NO 3 = ( ) 23 f. un. Al NO mol Al( NO 3 ) 3 = f. un. Al( NO 3 ) 3 3. How many molecules of iodine is equal to 2.14 x 10 3 moles of iodine? # mol x Avogadro s cf = # of molecules mol I molec I 2 1 mol I 2 = molec I 2 = molec I 2 2) Required Practice 4: Convert these mole amounts to number of particles of the compound indicated. Show all your work!! {Answers are on page 4.} mol NaCl mol H 2 O mol CaS 2 O mol OBr mol Ni 2 (SO 3 ) x 10 2 mol N 2 O x 10 4 mol HCl x 10 1 mol CH 3 OH x 10 7 mol Sr(OH) x 10 5 mol C 2 H 5 OH

4 CH 11 T36 COMPOUND CONVERSIONS & AVOGADRO S NUMBER 4 C) CONVERTING NUMBER OF MOLECULES OR FORMULA UNITS TO MOLES # of molecules or formula units x Avogadro s cf = # mol 1) Sample Problems x molecules of P 2 is equal to how many moles of P 2? # of molecules x Avogadro s cf = # mol molec P 2 1 mol P molec P 2 = mol P 2 = mol P x Al(NO 3 ) 3 formula units converts to how many moles Al(NO 3 ) 3? # Formula Units x Avogadro s cf = # mol f. un. Al( NO 3 ) 3 1 mol Al NO f. un. Al NO 3 = mol Al NO 3 = 9.0 mol Al( NO 3 ) x molecules of bromine is equal to how many moles of bromine? # of molecules x Avogadro s cf = # mol molec Br 2 1 mol Br molec Br 2 = mol Br 2 = mol Br 2 2) Required Practice 5: Convert the number of compound particles indicated to number of moles. your work!! {Answers are on page 4.} Show all x NaCl x molecules H 2 O x CaS 2 O x molecules OBr x Ni 2 (SO 3 ) x molecules N 2 O x molecules HCl x molecules CH 3 OH x Sr(OH) x molecules C 2 H 5 OH Required Practice 2 from page 2 ANSWERS TO THE REQUIRED PRACTICE N atoms 2. 9 NH + 4 ions; H atoms x atoms. 2.6 x N atoms x atoms x ions x OH ions x atoms O x atoms Required Practice 3 from page molecules N 2 O formula units (NH 4 ) 3 P x formula units (NH 4 ) 3 P x formula units (NH 4 ) 3 P x molecules H 2 O 2 Required Practice 4 from page x formula units NaCl x formula units CaS 2 O x formula units Ni 2 (SO 3 ) x molecules HCl x formula units Sr(OH) x H 2 O 2 molecules x molecules OBr x N 2 O molecules x molecules CH 3 OH x molecules C 2 H 5 OH Required Practice 5 from page mol NaCl x 10 4 mol CaS 2 O mol Ni 2 (SO 3 ) mol HCl x 10 6 mol Sr(OH) x 10 4 mol H 2 O x 10 6 mol OBr mol N 2 O x 10 5 mol CH 3 OH mol C 2 H 5 OH

5 CH 11 T36 COMPOUND CONVERSIONS & AVOGADRO S NUMBER 5 ASSIGNMENT At the top of your assignment, please print T36 Compound Conversions & Avogadro s Number, your LAST then First name, block and date. Show all your work for questions requiring calculations; marks will not be awarded for final answers only. Complete these questions in the order given here. [Marks indicated in italicized brackets.] x molecules of C 12 H 22 O 11(s) contain how many hydrogen atoms? [2] 2. How many lead(ii) thiosulphate formula units can be made from 4.2 x sulphur atoms? [2] 3. Calculate the number of oxygen molecules in 1.5 moles of oxygen gas. [2] 4. How many formula units of manganese(iv) oxide are in mole of the compound? [2] 5. How many molecules are in mol of nitrogen gas? [2] x formula units of aluminum sulphate contain how many moles of the compound? [2] [12 marks in total]