# C3H7OH is propanol. Suppose you have 85.9 g sample of propanol. How many carbon atoms are in the sample?

##### 2 Answers

I got:

#### Explanation:

The molecular formula of propanol is

First, we should calculate its molecular mass. I prefer to work with rounded numbers because that's how I was taught and frankly it makes life much easier. You should have memorised that the molar masses of carbon, hydrogen and oxygen are, respectively,

So let's add all that up:

#M = (3*12)+(8*1)+(1*16)#

#M = 60g/(mol)#

Okay, but that doesn't tell us much by itself. Elements make up substances in different proportions, because they have different masses, so how much of propanol is actually carbon, in terms of percentage? Remember,

#{:(60g -> 100%), (36g -> x%) :}} implies x = 60%#

So now we know that any given sample of propanol is sixty percent carbon. Now we can use the information that we were given:

#{: (85.9g -> 100%), (ycolor(white)(x)g -> 60%) :}} implies y = 51.54g#

Now, let us return to the concept of a mole. A mole is a quantity of

My answer might be different from somebody else's because, as I said, I prefer to work with simpler values. I hope, however, that the logic is clear! Cheers.

The number of carbon atoms in an 85.9 g sample of propanol is

#### Explanation:

Propanol:

The molar masses of carbon, hydrogen, and oxygen are:

**Identify the Molar Masses of Propanol and Carbon**

Molar mass of propanol:

Molar mass of carbon:

**Determine the Percentage of Carbon**

**Determine the Mass of Carbon in 85.9 g of Propanol**

In order to determine the mass of carbon present in 85.9 g propanol, we need to multiply the mass of propanol times the percentage of carbon as a decimal (e.g.

There are

**Determining the Number of Carbon Atoms**

Use the mass of carbon in the compound and carbon's molar mass to convert to moles of carbon. Then multiply the moles of carbon times