Stoichiometry

Stoichiometry

mass A ➔ mole A

mole A ➔ mole B

mole B ➔ mass B

mass A ➔ mass B

Goal

• Review everything you've seen so far.

• Recognize the different types of conversions

• Not get confused and mix up the different conversions

Multiple Choice

What type of conversion is this problem?

"How many mole of H₂O is 2.57 g of H₂O ?"

• mass A ➔ mole A

• mole A ➔ mole B

• mole A ➔ mass A

• mass A ➔ mass B

Mole A ➔ Mass A

"How many mole of H₂O is 2.57 g of H₂O ?"

The starting unit always has a number with it. The ending unit usually has a question with it.

Since this is starting with grams (mass) and asks to change to mole it

is a "mass ➔ mole" conversion.

Since this is starting with H₂O and ending with H₂O, then the substance (A) isn't changing. So it is a "mass A ➔ mole A" conversion.

Multiple Select

Check all problems that are "mass A ➔ mole A" conversions.

• Convert 3.64 g of Zn to mole of Zn

• How many grams is 2.83 mole of NaCl?

• Calculate the moles of H₂ produced from decomposing 5.40 mole of H₂O.

• Determine the number of moles of O₂ in 93.50 g of O₂.

• How many grams of CO₂ are produced from combustion with 5.00 g of CH₄?

Try a different problem

Multiple Choice

What kind of conversion is this problem?

"For this reaction:

2 NaCl ➔ 2 Na + Cl₂

How many moles of Cl₂ are produced from 3.45 moles of NaCl?"

• mass A ➔ mole A

• mole A ➔ mole B

• mole A ➔ mass A

• mass A ➔ mass B

Mole A ➔ Mole B

"For this reaction:

2 NaCl ➔ 2 Na + Cl₂

How many moles of Cl₂ are produced from 3.45 moles of NaCl?"

Since this question starts with moles and ends with moles, it

is a "mole ➔ mole" conversion.

Since this question converts from one substance into a different substance, it is a "mole A ➔ mole B" conversion.

Multiple Select

Check all problems that are "mole A ➔ mole B" conversions.

• Convert 3.64 g of Zn to mole of Zn

• How many grams is 2.83 mole of NaCl?

• Calculate the moles of H₂ produced from decomposing 5.40 mole of H₂O.

• Determine the number of moles of O₂ in 93.50 g of O₂.

• How many grams of CO₂ are produced from combustion with 5.00 g of CH₄?

Try a different problem

Multiple Choice

What kind of conversion is this problem?

"Convert 7.23 moles of CO₂ to grams."

• mass A ➔ mole A

• mole A ➔ mole B

• mole A ➔ mass A

• mass A ➔ mass B

Mole A ➔ Mass A

"Convert 7.23 moles of CO₂ to grams."

Since this is starting with mole and asks to change to grams (mass) it

is a "mole ➔ mass" conversion.

Since this is starting with CO₂ and doesn't mention a different chemical, then the substance (A) isn't changing. So it is a "mole A ➔ mass A" conversion.

You could also call this "mole B ➔ mass B" and it would be the same.

Multiple Select

Check all problems that are "mole A ➔ mass A" conversions.

• Convert 3.64 g of Zn to mole of Zn

• How many grams is 2.83 mole of NaCl?

• Calculate the moles of H₂ produced from decomposing 5.40 mole of H₂O.

• Determine the number of moles of O₂ in 93.50 g of O₂.

• How many grams of CO₂ are produced from combustion with 5.00 g of CH₄?

Now we'll look at "conversion factors"

• A conversion factor is the tool we use to make a conversion.

• If we have 8 quarters, how many dollars are there?

• This problem is a quarters ➔ dollars problem and the conversion factor is: 4 quarters = 1 dollar

Multiple Choice

Which conversion factor does this problem need?

"How many mole of H₂O is 2.57 g of H₂O ?"

• mole ratio O₂ : H₂O

• molar mass H₂O

• Balance H₂O

• molar mass O₂

Molar mass

"How many mole of H₂O is 2.57 g of H₂O?"

1 mole H₂O = 18.02 g H₂O

There are two different conversion factors:

Molar mass - converts between moles A and mass (grams) A, the substance must be the same!

Mole Ratio - converts between moles A and moles B, the substances are different but they are both in moles!

Molar mass is used whenever a problem has both mole and mass (grams)

"How many mole of H₂O is 2.57 g of H₂O?"

This is a mass A ➔ mole A conversion. So it uses molar mass.

but also

"Convert 7.23 moles of CO₂ to grams."

This is a mole A ➔ mass A conversion, so it also uses molar mass.

Multiple Select

Check all problems that would use the molar mass conversion factor.

• How many moles of NaCl are produced from the synthesis of 3.72 mole of Cl₂?

• How many grams are in 8.13 mole of Na?

• How many mole of H₂O are in 71.50 g of H₂O?

• How many mole of H₂O are produced from combustion of 1.50 mole of CH₄?

• How many mole of Zn are needed to produce 50 mole of ZnO?

Multiple Choice

Which conversion factor does this problem need?

"For this reaction:

2 NaCl ➔ 2 Na + Cl₂

How many moles of Cl₂ are produced from 3.45 moles of NaCl?"

• mole ratio NaCl : Cl₂

• molar mass NaCl

• Balance Cl₂

• molar mass Cl₂

Mole Ratio

"For this reaction:

2 NaCl ➔ 2 Na + Cl₂

How many moles of Cl₂ are produced from 3.45 moles of NaCl?"

There are two different conversion factors:

Molar mass - converts between moles A and mass (grams) A, the substance must be the same!

Mole Ratio - converts between moles A and moles B, the substances are different but they are both in moles!

Multiple Select

Check all problems that would use the mole ratio conversion factor.

• How many moles of NaCl are produced from the synthesis of 3.72 mole of Cl₂?

• How many grams are in 8.13 mole of Na?

• How many mole of H₂O are in 71.50 g of H₂O?

• How many mole of H₂O are produced from combustion of 1.50 mole of CH₄?

• How many mole of Zn are needed to produce 50 mole of ZnO?

Last Thing!

Multiple Choice

What kind of conversion is this problem?

"If you decompose 50 g of H₂O, how many grams of O₂ will you produce?"

• mass A ➔ mole A

• mole A ➔ mole B

• mole A ➔ mass A

• mass A ➔ mass B

Mass A ➔ Mass B

"If you decompose 50 g of H₂O, how many grams of O₂ will you produce?"

Since the conversion starts with grams and asks to change to grams, then the conversion is "mass ➔ mass"

Since the conversion starts with H₂O (A) and asks to change to O₂ (B), then the conversion is "mass A ➔ mass B"

Put it all together to make a

"mass A ➔ mass B" conversion.

mass A ➔ mass B

is the same as

mass A        ➔        mole A        ➔        mole B        ➔        mass B

        (molar mass A)      (mole ratio A:B)      (molar mass B)

So you would need 3 conversion factors, shown above

Multiple Select

Check all conversion factors that would be used to solve the problem:

"For the reaction: CH₄ + 2 O₂ ➔ CO₂ + 2 H₂O

How many grams of O₂ will react with 75.00 g of CH₄?"

• 1 mole CH₄ =

  16.05 g CH₄

• 1 mole O₂ =

  32.00 g O₂

• 1 mole CO₂ =

  44.01 g CO₂

• 1 mole CH₄ =

  2 mole O₂

• 1 mole CH₄ =

  1 mole CO₂

Done!

Take the quizziz quiz and see how you do

(it's not a major grade, so don't stress)