3.2 - Introducing the Mole - The Central Unit of Chemistry

Question 1

What form of mass is indicated for each element on the periodic table?

Answer 1

Relative Atomic Mass.

Question 2

When you have several elements in the amount of their respective relative atomic masses, each element would have the same number of ______?

Answer 2

Particles.

Question 3

The mole is a unit of what?

Answer 3

Magnitude (quantity).

Question 4

What do you call the SI unit for the quantity of atoms in exactly 12 g of pure carbon-12?

Answer 4

The mole.

Question 5

What is the unit symbol for the mole?

Answer 5

mol

Question 6

Is a mole an estimated measurement or a “counted value”

Answer 6

Estimate, affects sig figs.

Question 7

What is the name for the number of things in one mole?

Answer 7

Avogadro’s constant.

Question 8

What is the value of one mole?

Answer 8

6.02 x 10 ^23

Question 9

What are the two possible conversion factors for avogadro’s constant?

Answer 9

1 mol/6.02 x 10^23 items or 6.02 x 10^23 items/1 mol

Question 10

What do you call the mass of one mole of substance (particles can be atoms, ions, or molecules)

Answer 10

Molar mass.

Question 11

What is the unit symbol for molar mass?

Answer 11

g/mol.

Question 12

Why is molar mass unique to every substance?

Answer 12

atoms/molecules range in size/mass, therefore a mole of them will have different masses depending on what the particles are.

Question 13

How do you find the molar mass of an element on the periodic table?

Answer 13

Take its relative atomic mass and assign the unit g/mol as relative atomic mass = molar mass.

Question 14

How do you find the molar mass of a compound?

Answer 14

Calculate the molar mass of a compound by adding up the molar masses of its individual atoms.

Question 15

What do you need to know to calculate a compound’s molar mass?

Answer 15

• Which elements are present.
• # of atoms in each element.
• Each element’s molar mass.

Question 16

When calculating a compound’s molar mass, do you use the sig fig rules for addition or multiplication?

Answer 16

Addition (you are adding their values all up for your final answer).

Question 17

Molar masses should be to what decimal place?

Answer 17

1 decimal place.

Question 18

What is the most common mistake in calculating a compound’s molar mass?

Answer 18

Miscounting the atoms in each element (subscripts of bracketed symbols apply to everything in the brackets).

Question 19

When finding the molar mass of a hydrate, do you include the water portion of the compound?

Answer 19

Yes, because it’s molecules are considered part of the compound.

Question 20

What is the relationship between mass and moles of a substance?

Answer 20

1 molar mass g = 1 mol

Question 21

What are the conversion factors for molar mass and moles?

Answer 21

molar mass g/1 mol or 1 mol/molar mass g

Question 22

Which part of the mass/mole conversion factor is constant and what changes based off the substance?

Answer 22

1 mole is constant, the molar mass changes with each substance.