How big is a mole?

How big is a mole?

Not the furry kind.

Multiple Choice

How many donuts are in a dozen

• 2

• 12

• 13

• 6.02x10²³

Multiple Choice

How many donuts are in a baker's dozen?

• 2

• 12

• 13

• 6.02x10²³

Multiple Choice

How many donuts are in a mole?

• 2

• 12

• 13

• 6.02x10²³

Multiple Choice

Why is a number like Avogadro's Number, which is 6.02x10²³ need quantify an amount of atoms?

• Scientist like crazy numbers

• atoms and molecules are so small that it requires a stupendous amount of them so we can observe or measure them.

Multiple Choice

A mole of any item, has what number of those items?

• 6.02x10²³

• 5

Multiple Choice

Which of the follow best explains what the 10²³ in 6.02x10²³ ?

• it is part of scientific notation and it means there are 23 decimal places after the decimal.

• it is part of scientific notation and it means there are 23 decimal places after the 2 in the 6.02.

• it means 10 in multiplied 23 times.

Multiple Choice

If you have 2.5 moles of carbon. How many total atoms of carbon is there?

• $$6.02x10^{23}\ \div2.5$$

• $$\left(2.5\ x\ 6.02\right)\ x10^{23}$$

• $$2.5\ \left(6.02x10^{23}\right)$$

Multiple Choice

How many moles is  $$7.11x10^{24}$$   atoms of Ca?

• $$6.02x10^{23}\ \times7.11x10^{24}\ =moles$$  

• $$7.11x10^{24}\ \div6.02x10^{23}=Moles$$  

Multiple Choice

Butane gas produce $$\frac{310kJ}{mole}$$ of energy when burned What does the measurement $$\frac{310kJ}{mole}$$   mean?

Note: Kj means kilojoules and is a unit of energy.

• For every $$6.022x10^{23}$$  molecules of butane produces 310kJ of energy.

• For every $$6.022x10^{23}$$  grams of butane produces 310kJ of energy.

• For every 310kJ of energy $$6.022x10^{23}$$  molecules of butane are produces .

​How can the mole be used in to help us understand chemistry?

​Let's review a few facts.

1. Atoms and molecules ​are unimaginably small.

   1. "there a​ there are more molecules in a bottle of water then there are bottles of water in all the oceans on earth

Even more mind bending:

1. There are 1.67 x 10²¹ or 1.67 sextillion water molecules in a drop of water.

2. There are 5.01 x 10²¹ or about 5 sextillion atoms in a drop of water.

​

These numbers are incomprehensible to our human brains​.

Yet, as chemistry students, we need to understand and use atoms and molecules to ​all the time.​

Mass and moles-atoms

Here is how we measure our moles.

It turns out the the atomic mas of any element in grams is 1 mole of that element.

So, the atomic mass of carbon is​ 12.011 amu.

Therefore, 12.011g of carbon = 1 mole or 6.022x10²³atoms of carbon.

​Calcium has an atomic mass of 40.08 amu so 1 mole of Ca has a mass of 40.08g

​

Let's have you practice.​

Mass andMoles

It's easier to measure mass then to try to count the individual particles.

Multiple Choice

Which element will have a molar mass of 35.453g per mole?

• chlorine

• bromine

• irridium

• potassium

Multiple Choice

I mole of iron (Fe) has what mass in grams?

• 26g

• 81.845g

• 55.845g

Multiple Choice

What is the mass of 2 moles of the element oxygen (O)?

• 16g

• 31.998g

• 24.00g

• 63.996g

Multiple Choice

The element nitrogen (N) has a molar mass of 14.007g per mole. What is the mass of 1/2 of a mole of nitrogen? 

• 7.004g

• $$6.022x10^{23}\ \div2$$  

• 14.007g

Moles and Mass-compounds

Definition of molar mass- The mass in grams of any element or compound is equal to 1 mole.

Nitrogen gas has the molecular formula of N₂. The molar mass can be calculated by:

​atomic mass of nitrogen= 14.007amu, Since there are 2 nitrogen atoms in the formula N_2, 14.007 x2 = 28.014. Simply write this as a molar mass like this: 28.014g N₂ per mole or 28.014/mole.

​Another example​:

table salt has a formula of NaCl. To find the molar mass add the atomic mass of Na and Cl and then write as grams per mole.

Na= 22.990amu

Cl= +35.453amu​

58.443g per mole or 58.443g​

mole​​

Let's try some practice problems.

Multiple Choice

Which is the correct way to find the molar mass of ammonia with the formula of NH₃?

• H= 1.008

  N+14.007

  15.015gNH₃

  mole

• H= 3(1.008)=3.024

  N= +14.007

  17.031g NH₃

  mole

• H= 1.008

  N+14.007

  3(15.015gNH₃)

  mole

Multiple Choice

Find the molar mass of potassium oxide with the formula K₂O.

• 110.194g K₂O

  mole

• 71.096g K₂O

  mole

• 94.195g K2O

  mole

Summary

So why moles?

We measure moles by mass because mass is easy to measure in lab.

It would be impossible to count individual atoms or molecules because they are so small.

If we could count atoms of molecules at a rate of 10 million per second it​ it would take 2 billion years to the atoms in one mole. Who has that kind of time?

​

Moles be crazy!

Multiple Select

Select all the answers that best explains why we measure moles by find the mass?

• mass is easy to measure and calculate.

• Individual atoms and molecules are too small to measure.

• Since atoms are so small it would take forever to count 1 mole of them.