Moles Counting Unit in Chemistry

Agenda: Size of Atoms Moles: a counting unit in chemistry  What is a mole?  Why do we use moles?  Mole calculations Factor Label Method

Atoms are very, very small particles Too small to see To small to use an optical microscope Use a scanning tunneling microscope that is able to detect the electron clouds (due to the negative charge of the electrons)

Size of Atoms: Diameter Some estimates Atoms including the electron cloud  1 x 10 ⁻¹⁰ meters Nucleus  1 x 10 ⁻¹²m Proton  1 x 10 ⁻¹³ m (note: mass: 1x 672 x 10⁻²⁴g) Electron  1 x 10⁻¹⁶m

Atoms are so small: 1 x 10 ⁻¹⁰ meters Quarks to Quasars, Powers of Ten Quarks to Quasars, Powers of Ten

Review: Scientific Notation: aka: exponents, power of ten, etc. Positive exponents:  1 x 10 ⁶ atoms Negative exponents:  1 x 10 ⁻⁶ atoms Multiplying with exponents:  (1.5 x 10³ atoms) x ( 4.2 x 10⁶ atoms)  (3.4 x 10³ atoms) x (2.0 x 10⁻⁶ atoms) Dividing with exponents:  (1.5 x 10³ atoms) / ( 4.2 x 10⁶ atoms)  (3.4 x 10³ atoms) / (2.0 x 10⁻⁶ atoms) More information: Appendix near the back of the textbook

Moles Counting Unit in Chemistry

Alternative names for numbers Gross of pencils

The Mole and Avogadro’s Number What is a mole in chemistry? How much is a mole?  - Why are moles used?

Moles Why are moles used? How are they measured? (Standards)  The amount of substance that contains as many particles as there are in exactly 12 grams of C-12.  The amount of substance that contains Avogadro’s number of particles.  Molar mass – using the Periodic Table

Salt particle- NaCl Model of NaCl as an ionic compound Each salt particle in this photomicrograph would require the model to be multiplied by 10 ⁶ or more Formula Unit: NaCl Represents the repeating units that make up an ionic compound Such as NaCl, CaCl, Al₂O₃ New Term

Amounts: How can we determine the amount of salt particles in this picture?

Mole Conversions (Factor Label Method) Moles ↔ Grams 3.5 moles of He = ? Grams 40 grams of He = ? Moles Molar mass: 1 mole of He = ? Grams

Mole Conversions Moles ↔ Particles (atoms, molecules, compounds, etc.) 3.5 moles of He = ? Atoms x 10 ² ³ atoms of He = ? Moles 1 mole = atoms Review scientific notation

Mole Conversions Moles ↔ Volume of Gas (at STP) 3.5 moles of He = ? Liters 100 Liters of He = ? Moles 1 mole of a gas = Liters

Mole Flow Chart Mole

Practice problems: Moles and Mass What is the mass of 0.5 moles of S? How many grams is equivalent to moles of Fe? 4.63 mol P = ? grams P

Practice problems How many moles are in 84.3 grams of Si? 50 grams of Ne = ? moles of Ne

Mole and Atom Conversions How many atoms of Al are in 2.5 moles? How many atoms of Ag are in 0.26 moles? How many atoms of He are in moles?

Mole and Atom Conversion How many moles of P contains 1.0 x 10 ² ³ atoms? How many moles of Au are in 2.8 x 10 ² º atoms?

Moles, Moles, Moles Lab Sample in a jar Mass Moles Atoms 1 mole = ? grams 1 mole = ? atoms

Molar Mass of Compounds NaOHH ₃PO₄ H₂OPCl₃ MgCl₂H₂SO₄

Mole Conversion of Compounds How many grams are in 5 moles of CO ₂ ? How many atoms are in 5 moles of CO ₂ ? How many liters are in 5 moles of CO ₂ ?

A Mole is a Number

Review

Carbon has 6 protons