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**The Mole: A Measurement of Matter**

Chapter 10.1 The Mole: A Measurement of Matter

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**Three ways of measuring things…count, mass, & volume. **

Examples: soda—6 pack soda—liter grapes--lbs

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**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

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**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

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Calculate

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**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?

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What is a Mole? A specified number of particles. Used by chemists x 1023 representative particles (Avagrado’s number). Representative particles can be atoms, molecules, or formula units. Ratio: 1 mole/6.02x1023 rep. particles

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**Scientific basis of the mole**

6.02x1023 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.

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**Atoms to moles How many moles in 1.25x1023 atoms of magnesium?**

Known; # of atoms = 1.25x1023 1 mole = 6.02x1023 atoms Mg. Unknown; moles of magnesium. Calculate…

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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 (C3H8)? Known: # of moles of C3H8 is mole = 6.02x1023 molecules C3H8. 1 molecule C3H8 = 11 atoms. Unknown: # of atoms.

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Calculate… Practice… How many atoms in 1.14 moles SO3? How many moles in 4.65x1024 molecules NO2?

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**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.

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**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 g of hydrogen atoms must have the same number of atoms.

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**Representative Particle**

Smallest unit in a substance Can be different things One atom (metals, atomic substances) One molecule (molecular compounds) One ion (charged atoms or molecules) One formula unit (ionic compounds)

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**Examples of Representative particles**

Substance Representative particle Formula Iron atom Fe Atomic nitrogen N Nitrogen gas molecule N2 water H2O Calcium ion ion Ca2+ Calcium fluoride Formula unit CaF2 glucose C6H12O6

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**Measuring Chemical Substances**

Using Avogadro’s number: a specific number of representative particles 6.02 x 1023 RP/mole Referred to as one mole (mol) Example: One mol water contains 6.02 x 1023 H20 molecules Example: one mole nitrogen gas…

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**Practice Q: how many moles does 1.25 x 1023 atoms of Mg represent?**

A: 1.25 x 1023 Mg atoms x (6.03 x 1023 RP)/mole = 0.2 moles Q: how many moles does 2.8 x 1024 atoms of silicon have? A: 2.8 x 1024 Si atoms/6.03 x 1023 RP/mole = 4.6 moles Q:Q: How many propane (C3H8) molecules are in 2.12 mol of C3H8 ? A: 2.12 moles x (6.03 x 1023 ) RP/mole = 12.8

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**Converting molecular Moles into Number of individual atoms**

Hint: when asked for # of atoms always do Moles #molecules #atoms

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**Practice Q: How many atoms are in 2.12 mol of C3H8 ?**

First calculate how many molecules A: 2.12 moles x (6.02 x 1023 RP)/mole= x 1023 RP = 1.28 x 1024 RP Then calculate how many atoms Each RP (C3H8) has 11 atoms/RP Multiply with 11: 1.28 x 1024 RP x 11 Atoms/Rp= 14.08 X 1024 atoms Clean all results to single digit number!!! 14.08 X → Atoms = 1.4 x 1025 atoms

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**Practice You have 4.65 x 1024 molecules of NO2? Q: How many atoms?**

A: RP NO2 has three atoms/molecule 3 atoms/molecule x 4.65 x 1024 molecules

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**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

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**Finding mass What is the mass of one mole O, P, K, S-33, 146C**

Atomic oxygen: g/mole Atomic phosphorus: g/mole Atomic potassium: g/mole Atomic S-33: g/mole Atomic 146C: g/mole

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**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

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**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 1023 atoms of Hydrogen have? Is one mole → 1.01 g Q: What is the mass of 2.34 x 1022 atoms of phosphorus? First find how many moles 2.34 x 1022 atoms x mole/6.02 x 1023 atoms = 0.04 moles P 0.04 moles P x g/mole = 1.24 g

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**Mass of a Mole of a Compound**

Example: SO3 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 SO3 weighs 80.1 g

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**Practice: find the molar masses**

Find the molar mass of Water Glucose Carbon dioxide

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**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 x1023 RP/mole x 1.11 moles = 6.7 x molecules glucose

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The Mole: A Measurement of Matter OBJECTIVES: Describe how Avogadro’s number is related to a mole of any substance.

The Mole: A Measurement of Matter OBJECTIVES: Describe how Avogadro’s number is related to a mole of any substance.

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