# Homework Help: Calculate the approximate frequency of the C-H bond

1. Aug 10, 2008

### hot2moli

Calculate the approximate frequency of the C-H bond, with the force constant of k = 500 N/m.

Use:
Frequency = (1/2pi) Sqrt(k/((m1m2)/(m1 m2)))

BUTT WHAT DO I USE FOR MY MASS VALUES??
I tried, 12.011g/mol and 1.01g/mol and that is incorrect.

2. Aug 10, 2008

### alphysicist

Re: frequency

Hi hot2moli,

You're missing a plus sign in this formula. Is that just a typo?

Well, those aren't masses; they don't have the right units. (Those are the factors to connect number of moles of carbon atoms to number of grams of carbon atoms, and the same for hydrogen.) The C-H bond is connecting two atoms, so you need the masses of those two atoms. How do you get the mass of a carbon atom, and the mass of a hydrogen atom? Do you see what units they have to be in?

3. Aug 11, 2008

### hot2moli

Re: frequency

Yes I understand but since its 1:1 you can just multiply it by 1mol correct? Then it's 12.01g and 1.01g?? Which is my method of solving but evidently incorrect... therefore how do you find the masses?

4. Aug 11, 2008

### alphysicist

Re: frequency

That's the first step; to determine that there is 12.01 grams in a mole of carbon atoms, and 1.01 grams in a mole of hydrogen atoms.

Next, how many atoms are in a mole of atoms? Once you know that, since you know 1 mole of Carbon has 12.01 grams, you can find the mass of just one atom of Carbon. Then do the same for hydrgoren.

Also, note that the force constant is given in N/m. Since a Newton is a kg m/s^2, you'll need to get the mass of the carbon and oxygen atoms in kilograms. What do you get?