Chapter 3 Part I lectures SV

# Chapter 3 Part I lectures SV - Chapter 3 page 1 I MOLES and...

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Chapter 3, page 1 1 I. MOLES and MASS - ATOMS In the real world, need way to quantify large amounts of an element 1 st - need way of counting larger quantities instead of counting indiv. atoms, we count moles of atoms 1 mole = 6.022 x 10 23 particles ( applies to atoms, molecules, bowling balls ) This is really a conversion factor: 1 mole 6.022 x 10 23 particles Example: Calculate the number of moles in 7 atoms of He? What about masses of large quantities? MOLAR MASS of an element = t h e m a s s ( i n g ) o f a m o l e o f a t o m s o f t h a t s u b s t a n c e ( also called the atomic weight ) Æ numerically, it has the same # as the mass of an atom in amu molar mass of bowling balls vs. beach balls vs. ping pong balls each sample has same # of balls, but have different total masses

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Chapter 3, page 2 2
Chapter 3, page 3 3 molar mass is a ratio ± can be used as a conversion factor Example: What is the mass (in grams) of 0.430 mol Fe? Example 2 How many moles are in a 2.351 g sample of Al? How many atoms are in 2.351g of Al?

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Chapter 3, page 4 II. MOLES and MASS - COMPOUNDS Can read a molecular formula 2 ways: 1 formula unit of NaCl 1 Na + combines in 1:1 ratio with 1 Cl - 1 molecule of CH 4 1 a t o m o f C b o n d s t o 4 a t o m s o f H OR 1 mol NaCl 1 mol Na + combines in a 1:1 ratio with 1 mol Cl - 1 mol CH 4 1 mol of C bonds to 4 mol of H t h e f o r m u l a g i v e s u s i n f o r m a t i o n a b o u t h o w moles of each e l e m e n t a r e c o m b i n e d t o g e t h e r ! ! ! The formulas provide us with conversion factors
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Chapter 3 Part I lectures SV - Chapter 3 page 1 I MOLES and...

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