How many MOLECULES of carbon dioxide are present in 3.94 grams of this compound ?

Answer 1

I assume you mean molecules of CO₂.

The first thing to do is find the molecular mass of carbon dioxide. Because one molecule has one carbon (12.00 g/mol) and two oxygens (16.00g/ mol x 2), the molecular mass is 12.00 + 32.00, or 44.00g/mol.

Now we know how many grams of CO₂ we can expect to find in 1 mol of CO₂ : 44 grams for every 1 mol. Because we’ve got less than 44 grams, we should expect to have less than 1 mol. In order to find out exactly how many mols we have, we have to divide 3.98/44.00, which equals 0.0905 mols.

Now that we know how many mols we have, we need to find out how many molecules are in our fraction of a mol. To do this, we multiply 0.0905 x 6.022*10²³. This is because a mol is an abstract quantity that has 6.022*10²³ particles in it. So going back to our expression: 0.0905 x 6.022*10²³ = 5.45*10²² molecules.

The next time you have a problem like this:

1. Find the atomic mass of your element or molar mass of your compound.
2. Convert your sample from grams to mols using the atomic/molar mass.
3. Convert your sample from mols to particles using Avogadro’s number (6.022*10²³).
4. Additional step: if your sample is a COMPOUND and the problem is asking for the number of ATOMS, multiply the number you got from step 3 by the number of atoms in the compound.

Answer 2

1st: Convert mass(g) to mols for CO2

2nd: Convert mols to molecules for CO2

CO2 (Molar Mass) = 44.01 g/mol

3.94 g * (mol/ 44.01g) = 0.089525108 mols CO2

Now use Avogadro's # to convert mols to molecules

0.089525108 mols * (6.022 * 10^23 molecules/mol) = 5.39 * 10^22 molecules CO2

Answer 3