Would you mind checking these mole/unit conversion problems over? I understood them in class today, but that was hours ago, so now I need to start all over again.
How many moles of GaBr3 are in 983 grams? I got 983g times 1mole/309.42, which equaled 3.18. Is this correct? If not, could you explain the correct way?
One more. How many molecules are in 3.4 grams of H2? I set up the proportion so it read: 3.4 grams times 1 molecule/2 grams.
Thanks for your explanations.
#1 is correct.
#2 is not but you're half way there.
3.4 g H2 x (1 mole H2/2 g H2) = 1.7 moles H2. Now convert that to molecules. You must remember that 1 mole of H2 is 2 grams of H2 (or 22.4 L of the gas) but a mole and a molecule are not the same thing. 1 mole of H2 contains 6.02 x 10^23 molecules.
Thanks for the explanation. WOuld the answer then be 10.23?
hardly 10.23.
3.4 g H2 x (1 mole H2/2.016 g H2) x (6.022 x 10^23 molecules H2/1 mole H2) = 1.016 x 10^24 which rounds to 1.0 x 10^24 to two significant figures.
Sure, I'd be happy to help you check your mole/unit conversion problems and explain the correct way to solve them!
Let's start with the first problem:
Problem 1: How many moles of GaBr3 are in 983 grams?
To solve this problem, you need to use the molar mass of GaBr3, which is calculated by adding up the atomic masses of the elements involved (gallium and bromine). Based on the periodic table, the atomic mass of Ga is 69.72 g/mol, and the atomic mass of Br is 79.90 g/mol. So the molar mass of GaBr3 is (69.72 g/mol) + 3 * (79.90 g/mol) = 309.42 g/mol.
Now, to convert grams to moles, you need to divide the given mass by the molar mass. So, the correct calculation would be:
983 g / 309.42 g/mol = 3.177 moles (rounded to three decimal places)
Hence, your answer of 3.18 is indeed correct. Good job!
Now, let's move on to the second problem:
Problem 2: How many molecules are in 3.4 grams of H2?
To solve this problem, you need to again start by calculating the molar mass of H2, which consists of two hydrogen atoms. The atomic mass of hydrogen (H) is 1.01 g/mol. Since we have two hydrogen atoms, the molar mass of H2 is 2 * (1.01 g/mol) = 2.02 g/mol.
To convert grams to molecules, you'll need to use Avogadro's number, which represents the number of particles (molecules, atoms, etc.) in one mole of a substance. Avogadro's number is approximately 6.022 x 10^23 particles/mol.
To calculate the number of molecules in 3.4 grams of H2, you can use the following setup:
3.4 g H2 × (1 mol H2 / 2.02 g H2) × (6.022 x 10^23 molecules / 1 mol)
The units of grams H2 will cancel out, leaving you with molecules as the final unit.
Calculating this expression will give you the correct number of molecules in 3.4 grams of H2.
I hope this clears up any confusion you had. If you have any further questions or need additional explanations, feel free to ask!