Solution
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The molar mass of an element is determined by the atomic weight of that element, which can be found on the periodic table. The atomic weight of an element is the average mass of an atom of that element, measured in atomic mass units (amu).
Step 1: Locate Gold on the Periodic Table
Step 1: Locate Gold on the Periodic Table
Step 1: Locate Gold on the Periodic Table
Gold is represented by the symbol Au on the periodic table. It is located in period 6 and group 11.
Step 2: Identify the Atomic Weight
The atomic weight of gold is listed underneath the symbol Au. The atomic weight of gold is approximately 197.0 amu.
Step 3: Convert Atomic Weight to Molar Mass
The molar mass of an element in grams per mole is numerically equal to the element's atomic weight in atomic mass units. Therefore, the molar mass of gold is 197.0 grams per mole (g/mol).
So, the molar mass of gold (Au) is 197.0 g/mol. This means that one mole of gold has a mass of 197.0 grams.
Remember, a mole is a unit of measurement used in chemistry to express amounts of a chemical substance. It is defined as exactly 6.02214076×10^23 particles, which may be atoms, molecules, ions, or electrons.
In conclusion, understanding the molar mass of elements is crucial in chemistry, especially when dealing with reactions and stoichiometry. It allows chemists to make predictions about the amounts of substances involved in chemical reactions.
Gold is represented by the symbol Au on the periodic table. It is located in period 6 and group 11.
Step 2: Identify the Atomic Weight
The atomic weight of gold is listed underneath the symbol Au. The atomic weight of gold is approximately 197.0 amu.
Step 3: Convert Atomic Weight to Molar Mass
The molar mass of an element in grams per mole is numerically equal to the element's atomic weight in atomic mass units. Therefore, the molar mass of gold is 197.0 grams per mole (g/mol).
So, the molar mass of gold (Au) is 197.0 g/mol. This means that one mole of gold has a mass of 197.0 grams.
Remember, a mole is a unit of measurement used in chemistry to express amounts of a chemical substance. It is defined as exactly 6.02214076×10^23 particles, which may be atoms, molecules, ions, or electrons.
In conclusion, understanding the molar mass of elements is crucial in chemistry, especially when dealing with reactions and stoichiometry. It allows chemists to make predictions about the amounts of substances involved in chemical reactions.
Moles of Compounds and Elements
Exercise 1 Part a - Quantitative calculations with trinitrotoluene
Exercise 3 - Calculate the molar mass of FeCl₃
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In previous videos we talked about moles of atoms.
Here we're going to talk about moles of compounds and elements.
We learned that the molar mass of C^12 is exactly 12 grams.
We learned that the molar mass of oxygen,
taking into account the various isotopes,
is 15.999 grams, which is almost 16 grams.
Now we're going to learn how to calculate the molar mass of compounds.
If we have an empirical formula, or molecular formula,
or a formula unit,
all of which we've defined in previous videos.
We can find it's molar mass by adding
the molar masses of all the atoms that constitute the formula.
Let's take an example.
The first example we consider is NaCl,
which is sodium chloride,
which is ordinary salt.
You may remember in the previous video,
we said that this was an ionic solid,
consisting of Na plus cations and Cl minus anions.
Now the molar mass of NaCl,
consists of the molar mass of sodium,
plus the molar mass of chlorine.
If we add these 2 we should get the molar mass of sodium chloride.
This is its formula unit NaCl.
If we add 22.99 for sodium and 35.45 grams for chlorine,
we get 58.44 grams.
That's the molar mass of the formula unit, NaCl.
Now let's take another example.
Second example we're going to talk about is acetic acid,
CH_3CO_2H, which if we add up all the carbons,
and all the hydrogens,
we get C_2O_2 and H_4.
That's the molecular formula of acetic acid.
What the molar mass, you have to take twice the mass of carbon,
and twice the mass of oxygen,
because there are 2 carbons and 2 oxygens,
and 4 times the mass of hydrogen,
those are 4 hydrogens.
It's 2 times 12.01 plus 2 times 16.00 plus 4 times 1.008,
and altogether, that makes 60.05 grams So the molar mass of acetic acid is 60.05 grams,
and it's very important always to say molar mass of what?
I want to explain why it's important.
Let's consider the molar mass of oxygen.
Now the molar mass of oxygen,
the element, is 16.00 grams.
But the formula of oxygen gas isn't just O, it's O_2.
So that, the molar mass of O_2 is twice as much as 16.00 grams,
and that's 32.00 grams.
You can see how important is,
to say whether we're talking about O,
16.00 grams, or whether we're talking about O_2,
where it's 32.00 grams.
Now sometimes we're asked the number of molecules in a mole.
You'll recall, that in every mole,
there are Avogadro's number of units.
Let's take an example.
Once again, consider O_2.
Now Avogadro's number, 6.022 times 10^23.
There are 6.022 times 10^23 molecules in 1 mole of oxygen gas.
We can use the conversion factor,
1 mole of O_2 divided by 6.022 times 10^23 molecules of O_2,
and these are totally equivalent,
the ratio is 1, this conversion factor.
Let's take an example.
How many molecules are in 12 grams of O_2?
What we want to do is to go from grams,
to moles, and from moles to molecules.
The number of molecules is 12.00 grams of
oxygen times 1 mole of oxygen is gas is equivalent to 32.00 grams of oxygen,
so this is a conversion factor.
Then we want to convert moles to molecules.
So 6.022 times 10^23 molecules of O_2,
and 1 mole of oxygen is now a conversion factor.
If we multiply this out,
grams goes with grams of O_2,
moles of O_2, goes with moles of O_2,
we're left with molecules of O_2,
and that's 2.258 times 10^23 molecules of O_2.
Now we know precisely how many molecules of O_2 there are in 12 grams of oxygen.
In this video, we learned how to calculate
the molar mass and the number of molecules in a mole.
This video explains how to calculate the molar mass and the number of molecules in a mole of compounds and elements. It begins by discussing the molar mass of C^12 and oxygen, and then explains how to calculate the molar mass of compounds such as NaCl and acetic acid. It also explains how to calculate the number of molecules in a mole of a compound, using the example of oxygen gas.
• Molar mass of C^12 is 12 grams
• Molar mass of oxygen is 15.999 grams
• Molar mass of NaCl is 58.44 grams
• Molar mass of acetic acid is 60.05 grams
• Number of molecules in 1 mole of oxygen gas is 6.022 x 10^23
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