Unit #5 Polyatomic Ions / Mole / Molarity / Electrochemistry.

Unit #5Unit #5

Polyatomic Ions / Mole / Molarity / Electrochemistry

Polyatomic Ions / Mole / Molarity / Electrochemistry

This unit builds upon previous topics:

This unit builds upon previous topics:

Electron Configuration

Orbital Notation

Electron Dot Notation

Octet Rule

Electron Configuration

Orbital Notation

Electron Dot Notation

Octet Rule

Remember: Remember:

Ion- Ion- an atom or group of atoms that has either lost or gained electron(s) and as a result has an electric charge.

Cation- is a positively charged ion.

Anion- is a negatively charged ion.

Recall how we represented atoms with the electron dot notation.

Recall how we represented atoms with the electron dot notation.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

We will represent ions the same way with two exceptions:

1) If the atom has at least 5, but less than 8 valence electrons; we will draw as many additional electrons as needed to acquire a total of 8 valence electrons. (This will give the ion an Octet of valence electrons.)

1st exception con’t:1st exception con’t:

After the "atomic symbol" of the ion, in the upper right corner of the symbol, we will write a negative sign (or digit, if more than one) for each additional electron we added to achieve the nearest noble gas core. An octet of valence electrons.

After the "atomic symbol" of the ion, in the upper right corner of the symbol, we will write a negative sign (or digit, if more than one) for each additional electron we added to achieve the nearest noble gas core. An octet of valence electrons.


QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Example #1:


Example #2: Bromine


Example #3: Oxygen

We will represent ions the same way with two exceptions (con’t.):

2) If the atom has less than 4 valence electrons; we will remove as many electrons as needed to move back to the nearest noble gas core. A total of 8 valence electrons. (This will give the ion an Octet of valence electrons.)

2nd exception con’t:2nd exception con’t:

After the "atomic symbol" of the ion, in the upper right corner of the symbol, we will write a positive sign (or digit, if more than one) for each additional electron we subtracted to achieve the nearest noble gas core. An octet of valence electrons.

After the "atomic symbol" of the ion, in the upper right corner of the symbol, we will write a positive sign (or digit, if more than one) for each additional electron we subtracted to achieve the nearest noble gas core. An octet of valence electrons.


Example #1: SodiumExample #1: Sodium


Example #2: AluminumExample #2: Aluminum


Example #3: BariumExample #3: Barium

Polyatomic ion- Polyatomic ion-

A type of ion made of more than 2 atoms. These will also be classified as either an anion or a cation.

A type of ion made of more than 2 atoms. These will also be classified as either an anion or a cation.

4 steps to drawing polyatomic ions:

4 steps to drawing polyatomic ions:

Step 1) Determine and write down the "4 key numbers". Step 1) Determine and write down the "4 key numbers".

These are: pecv

"4 key numbers” (con’t.)"4 key numbers” (con’t.)

“p” # of protons (add up the atomic number of allinvolved atoms).

“p” # of protons (add up the atomic number of allinvolved atoms).

“e” # of total electrons (add up the atomic numbers (which equals the number of total electrons in a neutral atom) of all atoms in the ion.

"4 key numbers” (con’t.)"4 key numbers” (con’t.)

“c” # of core electrons (atomic number minus the number of "s" and "p" electrons in the highest energy level).

“c” # of core electrons (atomic number minus the number of "s" and "p" electrons in the highest energy level).

“v” # of valence electrons (determined bysubtracting the # of core

electrons from the # of total electrons).

Step 2)Step 2) Draw the "skeleton" of the ion

Step 3) Give all atoms eight electrons (except Hydrogen, it only wants two), (remember each bond (represented by a dash) counts as 2 electrons).

Step 4)Step 4) Count the number of electrons drawn and compare this to the calculated number ("Key number #4” the “v” ).

Adjust as necessary by adding double or triple bonds to reduce the number of electrons while still ensuring all atoms still have an octet of valence electrons.

Draw brackets and valence charge to finish.

Examples:

Examples:

AmmoniumCarbonateCyanide

The Mole Concept.The Mole Concept.

Mole - Mole -

The amount of substance that contains Avagadro's number of particles of that substance.

The amount of substance that contains Avagadro's number of particles of that substance.

Abbreviated: mol. NOT m, M, or M.

Avagadro's number - Avagadro's number -

This is equal to 6.02 * 1023 .This is equal to 6.02 * 1023 .

It is specifically the number of C12 atoms in 12 grams (the chart mass in grams) of this isotope.

Think of this word like the word "Dozen", which always means twelve. Well this number always means 6.02 * 1023 particles.

Atomic weight - Atomic weight -

The weighted average of the masses of the isotopes of an element.The weighted average of the masses of the isotopes of an element.

Based on C12 , 1 atom = 12 AMUs (atomic mass units).

AMU - arbitrary unit equal to 1/12 the mass of a C12 atom. (Atomic Mass Unit)

AMU continued:AMU continued:

Imagine if we had to determine the "weight" of everyone in the classroom, but, we didn't have a scale. We could select someone and then assign to that individual an arbitrary "weight" unit. We might say he/she weight 10 CRUs (Chem. Room Units). Everyone in the room will now be weighed relative to that student.

Imagine if we had to determine the "weight" of everyone in the classroom, but, we didn't have a scale. We could select someone and then assign to that individual an arbitrary "weight" unit. We might say he/she weight 10 CRUs (Chem. Room Units). Everyone in the room will now be weighed relative to that student.The atomic weight of all elements is relative to the "weight" of carbon 12.

Gram Atomic Weight - Gram Atomic Weight -

The mass in grams of 1 mole of a substance.The mass in grams of 1 mole of a substance.

Example 1: Hydrogen.

1 atom weighs ?

1 mole of hydrogen atoms weighs ?

However what is special about Hydrogen ?

1.0079 amu

1.0079 g.

Its diatomic

What is the formula for a molecule of Hydrogen?What is the formula for a molecule of Hydrogen?

1 molecule of Hydrogen weighs ?

1 mole of Hydrogen gas weighs ?

H2

2.0158 amu

2.0158 g.

Example #2: CO2Example #2: CO2

1 molecule of Carbon dioxide weighs ?

1 mole of Carbon dioxide weighs ?

44.0098 amu

44.0098 g.

Make sure you are aware of what you are working with:

Make sure you are aware of what you are working with:

Atoms or Molecules

AMUs or Grams

Molarity - Molarity -

Is a concentration unit in:#moles / liter. (The liter is usually water)

Is a concentration unit in:#moles / liter. (The liter is usually water)

Abbreviated: M NOT mol, M, m, or mol.

Note that the numerator is # of moles. We will learn how to convert this to grams in the next topic.

DIMO - DIMO -

An acronym that means:

Divide In Multiply Out.

An acronym that means:

Divide In Multiply Out.

It is a drawing that you have to be able to reproduce and use.

# of moles

# of grams # of particles

# of liters of a gas

Chart mass Avagadro’s #

22.4

4 Steps to use the DIMO chart.4 Steps to use the DIMO chart.

1 ) Determine the chart mass of thesubstance you're working with.

1 ) Determine the chart mass of thesubstance you're working with.

2) Deal with the concentration of that substance.

3) Deal with the volume of the solution you're working with.

4) Use "DIMO" to solve.

How many grams of NaOH are in 1 liter of a 1M solution of the NaOH?

Example 1:

STEP 1: Determine the chart mass

Example 1 (con’t.):

STEP 1: 40 g/mol

STEP 2: Deal with the concentration


STEP 1: 40 g/mol

STEP 2: 1 mol/L

STEP 3: Deal with the volume


STEP 1: 40 g/mol

STEP 2: 1 mol/L

STEP 3: 1 mol of NaOH in sample

STEP 4: Use "DIMO" to solve

How many grams of NaOH are in 1 liter of a 1M solution of the NaOH?

Solution to Example 1:

There are 40 g of NaOH in 1 liter of a 1M solution of NaOH.

0.75 liters of a 0.5M solution contains how many grams of CaCl2?

Example 2:



STEP 1: 111 g/mol



STEP 1: 111 g/mol

STEP 2: 0.5 mol/L



STEP 1: 111 g/mol

STEP 2: 0.5 mol/L

STEP 3:0.375 mol of CaCl2 in sample


How many grams of CaCl2 are in 0.75 liter of a 0.5M solution of the CaCl2?


There are 41.625 g of CaCl2 in 0.75 liter of a 0.5M solution of CaCl2.

Notice in the previous examples we calculated the number of grams of a substance.

In the next example, we will determine how many moles of a substance are in a given volume of a solution.

Notice in the previous examples we calculated the number of grams of a substance.

In the next example, we will determine how many moles of a substance are in a given volume of a solution.

What is the Molarity of a solution created by dissolving 150 grams of NaI into 250 mL of distilled water?

Example 3:



STEP 1: 150 g/mol



STEP 1: 150 g/mol

STEP 2: 150 g / 0.25 L



STEP 1: 150 g/mol

STEP 2: 150 g / 0.25 L

STEP 3: 600 g / 1 L


What is the Molarity of a solution created by dissolving 150 grams of NaI into 250 mL of distilled water?


There are 4 moles of NaI in 1 liter of the solution of NaI.

Therefore the molarity is ____4M

600 g of NaI is 4 moles

Finding the number of particles (atoms or

molecules) is done the same way: except you

would divide or multiply in or out by "Avagadro's

number".

You will get practice doing this on your study

guide.

Finding the number of particles (atoms or

molecules) is done the same way: except you

would divide or multiply in or out by "Avagadro's

number".

You will get practice doing this on your study

guide.

Unit #5 Polyatomic Ions / Mole / Molarity / Electrochemistry.

Documents

Transcript of Unit #5 Polyatomic Ions / Mole / Molarity / Electrochemistry.