Worksheet 1: REPRESENTATIVE PARTICLES

1 Worksheet 1: REPRESENTATIVE PARTICLES Directions: For each substance below, state the REPRESENTATIVE particle. If the RP is a molecule, state the number of atoms that make up the molecule. If the RP is a formula unit, state the number of ions that make up the formula unit. 1. NaCl _____ 2. H2SO4 _____ 3. K+ _____ 4. CaCl2 _____ 5. S _____ 6. S6 _____ 7. NH4Br _____ 8. Ca3(PO4)2 _____ 9. C6H12O11 _____ 10. Mg(NO3)2 _____ 11. Cl2 _____ 12. KMnO3 _____ 13. H2O2 _____ 14. H3PO3 _____ 15. NH4+ _____ 16. Fe2O3 _____ 17. NaC2H3O2 _____ 18. PO43- _____ 19. Hg _____ 20. O2- _____ Worksheet 2: THE MOLE AND AVOGADRO S NUMBER One mole of a substance contains Avogadro s Number ( X 1023) of molecules. How many molecules are in the quantities below? 1. moles 2. moles 3. mole 4. 15 moles 5. mole How many moles are in the number of molecules below?

2 1. x 1023 2. x 1024 3. x 1020 4. x 1026 5. x 1019 Worksheet 3: MOLAR MASS Determine the molar mass (the mass of one mole) of each compound below. Remember to include units (either amu or g/mol). Hint: for hydrated compounds such as CuSO4 5H2O, add the molar mass of the salt (CuSO4) to the mass of the number of water molecules indicated by the coefficient (5H2O = 5 water molecules). 1. KMnO4 _____ 2. KCl _____ 3. Na2SO4 _____ 4. Ca(NO3)2 _____ 5. Al2(SO4)3 _____ 6. (NH4)3PO4 _____ 7. CuSO4 5H2O _____ 8. Mg3(PO4)2 _____ 9. Zn(C2H3O2)2 2H2O _____ 10. Zn3(PO4)2 4H2O _____ 11. H2CO3 _____ 12. Hg2Cr2O7 _____ 13. Ba(ClO3)2 _____ 14. Fe2(SO3)3 _____ 15. NH4C2H3O2 _____ Worksheet 4: PERCENTAGE COMPOSITION Determine the percentage composition of each of the compounds below. Answers: Work: 1. KMnO4 K = _____ Mn = _____ O = _____ _____ 2. HCl H = _____ Cl = _____ _____ 3.

3 Mg(NO3)2 Mg = _____ N = _____ O = _____ _____ 4. (NH4)3PO4 N = _____ H = _____ P = _____ O = _____ _____ 5. Al2(SO4)3 Al = _____ S = _____ O = _____ _____ Solve the following problems. 6. How many grams of oxygen can be produced from the decomposition of 100 g of KClO3? _____ 7. How much iron can be recovered from g Fe2O3? _____ 8. How much silver can be recovered from 125 g of Ag2S? _____ Worksheet 5: Determining Empirical Formulas What is the empirical formula (lowest whole number ratio) of the compounds below? 1. 75% carbon, 25% hydrogen 2. potassium, chlorine 3. aluminum, phosphorus, oxygen 4. 13% magnesium, 87% bromine 5. sodium, sulfur, oxygen 6. copper, sulfur, oxygen, water Worksheet 5 continues onto the next ANSWER: ANSWER: ANSWER: ANSWER: ANSWER: ANSWER: Worksheet 5 Continued: Determining Molecular Formulas (True Formulas) 1.

4 The empirical formula of a compound is NO2. Its molecular mass is g/mol. What is its molecular formula? 2. The empirical formula of a compound is CH2. Its molecular mass is 70 g/mol. What is its molecular formula? 3. A compound is found to be carbon, hydrogen and oxygen. Its molecular mass is 60. g/mol. What is its molecular formula? 4. A compound is carbon, hydrogen and oxygen. Its molecular mass is 74 g/mol. What is its molecular formula? 5. A compound is carbon, hydrogen and oxygen. Its molecular mass is 88 g/mol. What is its molecular formula? ANSWER: ANSWER: ANSWER: ANSWER: ANSWER: Worksheet 6: COMPOSITION OF HYDRATES A hydrate is an ionic compound with water molecules loosely bonded to its crystal structure. The water is in a specific ratio to each formula unit of the salt. For example, the formula Na2S 9H2O indicates that there are nine water molecules for every one formula unit of Na2S.

5 Answer the questions below. 1. What percentage of water found in Na2S 9H2O? 2. A g sample of a hydrate of BaCl2 was heated, and only g of the anhydrous salt remained. What percentage of water was in the hydrate? 3. A g sample of a hydrate of Ca(NO3)2 was heated, and only g of the anhydrous salt remained. What percentage of water was in the hydrate? 4. A g sample of Na2CO3 H2O is heated to constant mass. How much anhydrous salt remains? 5. A g sample of Cu(NO3)2 nH2O is heated, and g of the anhydrous salt remains. What is the value of n? Worksheet 7: Chemical Quantities Review (CP) 1. Name the REPRESENTATIVE particle for the following substances: N _____ N+ _____ N2 _____ NaHCO3_____ CO2 _____ C6H6 _____ Na2SO4_____ NaOH _____ 2. Calculate the molar mass of each the following substances: C6H6 _____ Ca(NO3)2 _____ MgSO4 7H2O _____ 3.

6 How many moles are in g of HC2H3O2? 4. Calculate the mass of moles of CuSO4 5H2O. 5. How many molecules are in g N2O? 6. Calculate the volume of g of Cl2 gas at STP. 7. How many oxygen atoms are in molecules of HC7H5O2? 8. Calculate the mass of x 1015 molecules of CH4. 9. Calculate the percentage composition of Ca(OH)2. 10. How many grams of zinc could be extracted from kg (1000 g) of ZnCl2? HELPFUL TIPS FOR THE UPCOMING TEST ! Know the four REPRESENTATIVE PARTICLES and be able to determine what the is for a given substance. ! Know how to find the molar mass / molecular weight (MW) of a given substance. ! Know how to determine the number of atoms / ions present in one molecule or formula unit of a given substance. ! Know how to convert between units of mass, moles, volume, REPRESENTATIVE PARTICLES , and atoms or ions when appropriate. ! Know the values of standard temperature and pressure.

7 ! Know how to calculate percent composition. ! Know how to calculate the mass of some part of a compound that could be recovered. o For example, a typical bottle of fingernail polish contains mg of tin (IV) oxide. What mass of tin is present in this amount? ! Begin calculations with the given value. ! PAY ATTENTION TO UNITS ! Convert to the mole before converting to any other unit. ! Round to the tenth s place when calculating molar mass. ! Attach the appropriate units to all values. ! Give your answer with the same number of significant digits as the given value when converting between units. ! PAY ATTENTION TO UNITS ! Use Avogadro s number ( x 1023 REPRESENTATIVE PARTICLES / mole) to convert to and from REPRESENTATIVE PARTICLES . ! Use molar mass to convert to and from mass. ! Use molar volume ( L / mole) to convert to and from volume of a gas at STP. ! PAY ATTENTION TO UNITS !

8 Remember that density = mass (g) / volume (L) Remember: 1 mole = x 1023 s 1 mole = molar mass in grams 1 mole = L of gas @STP