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Mole Conversion Notes

Step 1: Begin by listing your known and unknown. Decide which conversion factor you should use

based on what the problem is asking you to find.

Step 2: Make a T-chart, and put whatever information the problem gave you in the top left. After

that, put the units of whatever you were given in the bottom right of the T, and the units of what

you want to find in the top right.

In this case, the problem gave you "22 grams of copper" as the starting information. Because this is

what you were given, put "22 grams of copper" in the top left of the T. Since "grams of copper" is

the unit of what you were given, put this in the bottom right of the T. Since you want to find out how

many moles of copper are going to be made, put "moles of copper" as your unit in the top right.

When you've done this, your calculation should look like this:

Step 2: Put the conversion factors into the T-chart in front of the units on the right.

Using the map, the conversion factor between grams and moles is the atomic mass of copper.

Because we measure atomic mass in grams, you need to put the atomic mass in front of the unit

"grams of copper". What do you put in front of moles? Whenever you do a calculation of this kind,

you need to put "1" in front of moles, like you see here:

Step 3: Cancel out the units from the top left and bottom right, and then find the answer by

multiplying all the stuff on the top together and dividing it by the stuff on the bottom.

In this case, you'd multiply 22 by one and divide the result by 63.5. Your answer is 0.35 moles of

copper:

And that's how you do a one-step problem of this kind!

Solving Two-Step Mole Calculation Problems:

What happens if we need to solve a problem that requires we not just go from one box in the next in

our diagram, but across the entire diagram? Well, it means that we need to do two steps in our

calculation. Let's see that "map" again to see what I mean:

If we were asked to convert 22 grams of copper to atoms of copper, we'd have to go from one end

of the map to the other. Instead of doing a simple one step calculation, we'd need to do a two-step

calculation, with the first step going from grams to moles and the second step going from moles to

atoms.

How can we solve this kind of problem? Well, we start off by doing the same thing that we did in our

last example: We had to convert grams to moles before, and we can see from the map that we have

to convert grams to moles now, too. To refresh your memory, here's the calculation from last time:

In the next step, we do the same thing over again, except that we need to add another T to the T-

chart. When you do this, take the units of the thing at the new top left and put them on the bottom

right (in this case, moles). Then take the units of what you want (in this case, atoms) and put it in the

top right. Finally, put in your conversion factors, which from the chart above is Avogadro's number,

or 6.02E23. Since this number refers to the number of atoms in a mole of a substance, we put this in

front of "atoms of copper". Again, put the number "1" in front of moles, because we're saying that

there are 6.02E23 atoms in ONE mole of an element.

When we add all these terms in, we can cross out the units that cancel out, as shown. To get the

answer, multiply all the numbers on the top together and divide by the numbers on the bottom. Your

answer should then be set up like this:

And that's how you do mole problems!

How do you convert from mass to moles? What is the formula for converting mass to moles? The atomic number of an element is the number of protons contained within each atom of that element. The atomic mass of an element is defined as the average total mass of one atom of that element. The atomic mass unit, abbreviated as amu, is the unit of atomic mass. It is estimated that one amu is equal to the mass of one proton or neutron. More items...

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