1. Chemical Quantities

2. 10.1

3. Key Question How can you convert among the count, mass, and volume of something? Knowing how the count, mass, and volume of an item relate to a common unit allows you to convert among these units. ROCK ME AVOGADRO! https://www.youtube.com/watch?v=13WUqWd_Yk8

4.  A mole (mol) of a substance is 6.02 x 10 23 representative particles (atom, molecule, ion, or formula unit) of that substance and is the SI unit for measuring the amount of a substance  The number of representative particles in a mole, 6.02 x 10 23, is called Avogadro’s number (N A )  It was named in honor of the Italian scientist Amedeo Avogadro, who helped clarify the difference between atoms and molecules  Representative particles refer to the species present in a substance, usually atoms, molecules, or formula units

5. Key Question How do chemists count the number of atoms, molecules, or formula units in a substance? The mole allows chemists to count the number of representative particles in a substance.

6. Table 10.1 summarizes the relationship between representative particles and moles of substances.

7. 1 mol = 6.02 x 10 23 representative particles Representative particles being an atom, a molecule, an ion, or a formula unit! A mole is always the same number, but 1-mole samples of different substances will have different masses Example: 1 mol of C and 1 mol of Mg C has a mass of ~12 amu Mg has a mass of ~24 amu

8. The mass of a single atom of an element is numerically equal to the mass of 1 mol of that element. Therefore, the molar mass (g/mol) of any substance is always equal to its formula or molecular weight.

9. PROBLEM SOLVING Step 1: Analyze the problem Step 2: Develop a plan for solving the problem Step 3: Solve the problem Step 4: Check the solution

10. Converting between Number of Particles and Moles IN CLASS ONLY!

11. Converting between Number of Particles and Moles *To find the number of atoms in a given number of moles of a compound, you must first determine the number of representative particles! IN CLASS ONLY!

12. Key Question How do you determine the molar mass of an element and of a compound? Of an element-The atomic mass of an element expressed in grams is the mass of a mole of the element.  The mass of a mole of an element is its molar mass. Of a compound-To calculate the molar mass of a compound, find the number of grams of each element in one mole of the compound. Then add the masses of the elements in the compound.

13. CC  12.011 g/mol HH  1.0079 g/mol SS  Al  He

14. H2OH2O  18.015 g/mol  CO  28.010 g/mol  CS 2  76.13 g/mol  CCl 4  153.823 g/mol  S 2 Cl 2  135.026 g/mol

15. 10.2

16. Key Question How do you convert the mass of a substance to the number of moles of the substance? Use the molar mass of an element or compound to convert between the mass of a substance and the moles of the substance Conversion Factor Molar mass = 1 mol ;therefore, mass and 1 mol 1 mol mass

17. IN CLASS ONLY!

18.  Avogadro’s hypothesis states that equal volumes of gases at the same temperature and pressure contain equal numbers of particles  The particles that make up different gases are not the same size  The volume of a gas varies with a change in temperature or a change in pressure; therefore, the volume of a gas is usually measured at a standard temperature and pressure  Standard Temperature and Pressure (STP) means a temperature of 273 K (0 oC), 1.0 atm (101.3 kPa, and 22.4 L  At STP 1 mol of any gas occupies a volume of 22.4 L  22.4 L is called the molar volume of a gas

19. How do you convert the volume of a gas at STP to the number of moles of the gas? The molar volume is used to convert between the number of moles of gas and the volume of the gas at STP. Conversion Factor 22.4 L = 1 mol at STP ;therefore, 22.4 L and 1 mol 1 mol 22.4 L

20. IN CLASS ONLY!

21.  Density is the ratio of the mass of an object to its volume Key Question What determines the density of a substance? Density is an intensive property that depends only on the composition of a substance  The SI units of density is g/cm 3 or g/L  The SI unit of mass is g  The SI unit of volume is cm 3 or L  The density of a gas is measured in g/L  The density of a gas at STP and the molar volume at STP can be used to calculate the molar mass of the gas, and the molar mass of a gas and the molar volume at STP can be used to calculate the density of a gas at STP

22. IN CLASS ONLY!

23. g  m  r p (grams, moles, repres. par.) and Vice Versa

24. 10.3

25.  Percent composition is the percent by mass of each element in the compound

26. How do you calculate the percent composition of a compound? The percent by mass of an element in a compound is the number of grams of the element divided by the mass in grams of the compound, multiplied by 100%.

27. % by mass of an element = mass of element x 100% mass of compound % by mass of element = mass of element in 1 mol compound x 100% molar mass of compound Practice IN CLASS ONLY!

28.  You can use percent composition to calculate the number of grams of any element in a specific mass of a compound  To do this, multiply the mass of the compound by a conversion factor based on the percent composition of the element in the compound

29. IN CLASS ONLY!

30.  Empirical formula of a compound gives the lowest whole-number ratio of the atoms or moles of the elements in a compound  The ratio of the number of moles of each element in a compound gives the subscripts in a compound’s empirical formula

31. How can you calculate the empirical formula of a compound? The percent composition of a compound can be used to calculate the empirical formula of that compound.

32. IN CLASS ONLY!

33. Key Question How does the molecular formula of a compound compare with the empirical formula ? The molecular formula of a compound is either the same as its experimentally determined empirical formula, or it is a simple whole-number multiple of its empirical formula.

34. Simple Whole-Number Multiple for Molecular Formulas is the molecular weight (molar mass of unknown) Empirical formula weight (molar mass of empirical formula) *Fractions of atoms do not exist in compounds. In the case where the ratio of atoms is a fractional number the ratio should be simplified by multiplying all the atoms by a constant to give whole number ratios for all the atoms

35. IN CLASS ONLY!