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Chapter 10.1 The Mole: A Measurement of Matter. ► Three ways of measuring things…count, mass, & volume. ► Examples: soda—6 pack ► soda—liter ► grapes--lbs.

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Presentation on theme: "Chapter 10.1 The Mole: A Measurement of Matter. ► Three ways of measuring things…count, mass, & volume. ► Examples: soda—6 pack ► soda—liter ► grapes--lbs."— Presentation transcript:

1 Chapter 10.1 The Mole: A Measurement of Matter

2 ► Three ways of measuring things…count, mass, & volume. ► Examples: soda—6 pack ► soda—liter ► grapes--lbs

3 ► Terms for specific counts…pair, dozen, etc. ► 1 dozen apples = 12 apples. ► 1 dozen apples = 2.0 kg apples. ► 1 dozen apples = 0.2 bushels apples. ► Ratios: 1 dozen apples/12 apples ► 1 dozen apples/2.0 kg apples ► 1 dozen apples/0.2 bushels apples

4 Problem… ► What is the mass of 90 apples if 1 dozen apples = 2.0 kg? ► Analyze…known… ► # of apples = 90 ► 12 apples = 1 dozen ► 1 dozen = 2.0 kg ► Unknown…mass of 90 apples = ?kg

5 Calculate

6 Evaluate ► Does it make sense? ► Practice…What is the mass of 0.5 bushels of apples? ► Practice…assume 8 seeds per apple. How many seeds are in 14 kg of apples?

7 What is a Mole? ► A specified number of particles. Used by chemists x representative particles (Avagrado’s number). ► Representative particles can be atoms, molecules, or formula units. ► Ratio: 1 mole/6.02x10 23 rep. particles

8 Scientific basis of the mole ► 6.02x10 23 is the number of atoms in 12 grams of Carbon-12. ► If one mole of carbon-12 atoms were weighed, it would weigh exactly 12 grams.

9 Atoms to moles ► How many moles in 1.25x10 23 atoms of magnesium? ► Known; # of atoms = 1.25x10 23 ► 1 mole = 6.02x10 23 atoms Mg. ► Unknown; moles of magnesium. ► Calculate…

10 Moles to # of particles ► How many atoms in a mole? First determine how many atoms in a representative particle. ► How many atoms in 2.12 moles of propane (C 3 H 8 )? ► Known: # of moles of C 3 H 8 is mole = 6.02x10 23 molecules C 3 H 8. 1 molecule C 3 H 8 = 11 atoms. ► Unknown: # of atoms.

11 ► Calculate… ► Practice… ► How many atoms in 1.14 moles SO 3 ? ► How many moles in 4.65x10 24 molecules NO 2 ?

12 The Mass of a Mole of an Element ► Mass of atoms expressed in amu’s (atomic mass units), which are relative units based on the isotope Carbon-12 (12.0 amu). ► C-12 is twelve times heavier than an average hydrogen atom with a mass of 1.0 amu. ► 100 C-12 atoms are 12 times heavier than 100 hydrogen atoms.

13 ► Any number of C-12 atoms are always twelve times heavier than the same number of hydrogen atoms. ► The mass ratio of 12 carbon atoms to 1 hydrogen atom is the same regardless of the units used to express the mass. ► Therefore, 12.0 g of carbon atoms and 1.0 g of hydrogen atoms must have the same number of atoms.

14 Representative Particle ► Smallest unit in a substance ► Can be different things 1. One atom (metals, atomic substances) 2. One molecule (molecular compounds) 3. One ion (charged atoms or molecules) 4. One formula unit (ionic compounds)

15 Examples of Representative particles Substance Representative particle Formula IronatomFe Atomic nitrogen atomN Nitrogen gas molecule N2N2N2N2 watermolecule H2OH2OH2OH2O Calcium ion ion Ca 2+ Calcium fluoride Formula unit CaF 2 glucosemolecule C 6 H 12 O 6

16 Measuring Chemical Substances ► Using Avogadro’s number: a specific number of representative particles 6.02 x RP/mole ► Referred to as one mole (mol) Example: One mol water contains ► 6.02 x H 2 0 molecules Example: one mole nitrogen gas…

17 Practice Q: how many moles does 1.25 x atoms of Mg represent? A: 1.25 x Mg atoms x (6.03 x RP)/mole = 0.2 moles Q: how many moles does 2.8 x atoms of silicon have? A: 2.8 x Si atoms/6.03 x RP/mole = 4.6 moles Q:Q: How many propane (C 3 H 8 ) molecules are in 2.12 mol of C 3 H 8 ? A: 2.12 moles x (6.03 x ) RP/mole = 12.8

18 Converting molecular Moles into Number of individual atoms Hint: when asked for # of atoms always do Moles #molecules #atoms

19 Practice Q: How many atoms are in 2.12 mol of C 3 H 8 ? ► First calculate how many molecules A: 2.12 moles x (6.02 x RP)/mole= x RP = 1.28 x RP ► Then calculate how many atoms Each RP (C 3 H 8 ) has 11 atoms/RP Multiply with 11: 1.28 x RP x 11 Atoms/Rp= X atoms ► Clean all results to single digit number!!! X → Atoms = 1.4 x atoms

20 Practice You have 4.65 x molecules of NO 2 ? Q: How many atoms? A: RP NO 2 has three atoms/molecule 3 atoms/molecule x 4.65 x molecules

21 The mass of one mole of a given element ► Mass of an element is indicated in the periodic table as the mass number ► Called amu = atomic mass unit ► amu is the mass (in grams) of one mole of this element ► Remember it is an average number of the different isotopes…it has decimals

22 Finding mass ► What is the mass of one mole O, P, K, S- 33, 14 6 C ► Atomic oxygen: g/mole ► Atomic phosphorus: g/mole ► Atomic potassium: g/mole ► Atomic S-33: g/mole ► Atomic 14 6 C: g/mole

23 How many mole in a given mass ► How many moles of Carbon are found in 52 g? ► 52 g/12.01 g/mole C= 4.33 moles C

24 Practice calculating molar masses Q: How many moles of C-14 are found in 34 g? ► 34 g x mole C-14/14g C-14 = 2.42 moles C-14 Q: What mass does 6.02 x atoms of Hydrogen have? ► Is one mole → 1.01 g Q: What is the mass of 2.34 x atoms of phosphorus? First find how many moles 2.34 x atoms x mole/6.02 x atoms = 0.04 moles P 0.04 moles P x g/mole = 1.24 g

25 Mass of a Mole of a Compound ► Example: SO 3 ► What type of compound? ► How many atoms of S and O? ► Add up amus of S and O ► 32.1 amu amu amu amu = 80.1 amu ► One mole SO 3 weighs 80.1 g

26 Practice: find the molar masses Find the molar mass of ► Water ► Glucose ► Carbon dioxide

27 Practice Q:How many moles of glucose are in 200 g? ► Molar mass of glucose is g/mole A: 200g x mole/ g = 1.11 moles Q: How many molecules of glucose is this? 6.02 x10 23 RP/mole x 1.11 moles = 6.7 x molecules glucose


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