6.02 x atoms (1 mole) has a mass of g (manageable mass)

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1 The Mole (read pages MHR Text P ) Reading a Balanced Chemical Equation Q. Write a balanced chemical equation for the formation of hydrazine, N 2 H 4, from its elements. N 2 +2 H 2 N 2 H 4 1 molecule of N molecules of H 2 1 molecule of N 2 H x particles + 2(6.022 x particles) x particles 1 mole+ 2 mole 1 mole Q. Why do scientist use such a large number? Since atoms, molecules and ions are extremely small particles, it is easier to use a large number when you are talking about their amounts (mass) Ex1: 1 atom of Oxygen has a mass of 2.65 x g (extremely small mass) 6.02 x atoms (1 mole) has a mass of g (manageable mass) Oct 4 6:39 PM 1

2 Ex 2: 1 molecule of sugar (C 12 H 22 O 11 ) has a mass of 5.69 x g (extremely small mass) 6.02 x molecules (1 mole) has a mass of g (manageable mass) Sep 25 4:20 PM 2

3 The Mole is 6.02 x particles (atoms, ions or molecules). Often referred to as Avagadro's number after the scientist who determined it. is the number of atoms in exactly 12 g of the most common isotope of carbon carbon 12. Types of particles: atoms in elements molecules in molecular compounds formula units in ionic compounds Mole n = N N A where n = # of moles N= # particles N A = Avagadro s Number = x particles/mol Oct 4 6:45 PM 3

4 Converting moles to number of particles or the opposite Ex1. How many atoms of Fe are in 0.50 mol of Fe? Ex 2. a)how many moles of CH 4 molecules are there in 9.0 x molecules of CH 4? b) How many atoms in CH 4? Oct 4 6:54 PM 4

5 Ex3: Consider a mol sample of potassium carbonate, K 2 CO 3. a) How many formula units are in the sample? b) How many potassium ions are in the sample? c) How many carbonate ions are in the sample? Oct 4 6:56 PM 5

6 Ex 4. A sample contains 1.25 moles of nitrogen dioxide,no 2? a) How many molecules are in the sample? b) How many atoms are in the sample? Oct 4 7:07 PM 6

7 Ex 5. a)how many moles of are present in a sample of carbon dioxide,co 2, made up of 5.83 x molecules? b)how many atoms are present in this sample? Oct 4 7:14 PM 7

8 Sep 29 9:09 PM 8

9 Molar Mass (Read MHR Text p ) How do chemists determine the number of moles in a sample? It is impossible to count the atoms, molecules, or ions in a sample. Chemists define Avagadro's number as the number of carbon atoms in exactly 12 grams of carbon 12. Accurately, there are x atoms of C 12 in 12 g. or 1 mole of C 12 has a mass of 12 g. Chemists then determine the mass of 1 mole of each element relative to carbon 12. These values are placed on the periodic table and are called the average atomic mass or molar mass Molar mass is the mass of one mole of particles of a substance. units are grams per mole, g/mol, g. mol 1 Oct 5 8:36 PM 9

10 1) Molar masses of elements are found on the periodic table. Ex:Molar mass of Na is g/mol Molar mass of Au is g/mol 2) Molar mass of a compound is found by determining the number of each element contained in the formula multiply that number by the element's molar mass add all molar masses together Oct 5 8:41 PM 10

11 a) Find molar mass of Na 2 CO 3 M Na 2 CO 3 = 2 x M Na = 2 x = x M C = 1 x = x M O = 3 x = g/mol b) Find molar mass of Mg(NO 3 ) 2 M Mg(NO 3 ) 2 = 1 x M Mg = 1 x = x M N = 2 x = x M O = 6 x = g/mol Oct 5 8:42 PM 11

12 c) Find molar mass of Al 2 (Cr 2 O 7 ) 3 M Al2 (Cr 2 O 7 ) = 2 x M Al = 2 x = x M Cr = 6 x = x M O = 21 x = g/mol d) Find the molar mass of CrCl 3. 6 H 2 O M CrCl 3 6H 2 O= 1 x M Cr = 1 x = x M Cl = 3 x = x M H = 12 x 1.01 = x M O = 6 x = g/mol Oct 5 8:43 PM 12

13 Moles to Mass Calculations (see MHR Text p ) 1.0 mol of oxygen atoms = g (molar mass) 0.50 mol of oxygen atoms =? g 2.0 mol of oxygen atoms =? g Mass = moles x molar mass Oct 11 5:01 PM 13

14 Formula: n = m n M m M where m = mass n = # of moles M = molar mass rearrange the equation to get m = n x M Oct 11 5:05 PM 14

15 Ex1. What is the mass of a 2.40 mol of aluminum nitrate? Oct 11 5:08 PM 15

16 2. What is the mass of 0.58 mol of iron (III) oxide? Oct 11 5:08 PM 16

17 Mass to Moles Calculations(see MHR Text p ) Ex1.Find the number of moles in 14.1 g of xenon hexafluoride Oct 11 5:09 PM 17

18 Ex2. Calculate the number of moles of 0.59 kg of lead (II) phosphide. Express answer in scientific notation. Oct 11 5:13 PM 18

19 Particles to Mass (see MHR Text p ) Ex1:What mass does 3.01 x atoms of potassium have? Oct 14 10:24 PM 19

20 Ex2:What mass does 8.96 x molecules of dinitrogen tetraoxide hav Oct 14 10:25 PM 20

21 Mass to Particles (see MHR Text p ) Ex1:How many atoms (particles) of calcium are in 5.00 g? Oct 14 10:28 PM 21

22 Ex 2:How many formula units does 10.0 g of magnesium hydroxide contain? Oct 14 10:29 PM 22

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24 Feb 5 1:05 PM 24

Average Atomic Mass. A new unit called the atomic mass unit (amu) was developed to deal with the very small units of mass for particles like the atom.

Average Atomic Mass. A new unit called the atomic mass unit (amu) was developed to deal with the very small units of mass for particles like the atom. Average Atomic Mass Since atoms are so small and the mass of individual atoms is also very small, it is not useful to use the units of grams or kilogram. A new unit called the atomic mass unit (amu) was