Molar Mass: E21

Emilee Hosking 1D
Posts: 32
Joined: Fri Sep 28, 2018 12:17 am

Molar Mass: E21

For question E21, it states, "Calculate the amount (in moles) and the number of molecules and formula units (or atoms if indicated) in a) 10.0g of alumni, Al[sub]2O[sub]3 b)25.92 mg of hydrogen flouride, HF; c) 1.55mg of hydrogen peroxide, H20; d) 1.25 kg of glucose, C[sub]6H[sub]12O[sub]6; e) 4.37 g of nitrogen as N atoms and as N[sub]2 molecules." I know that I should convert the kg and mg to grams so I have a consistent SI unit, but where do I go from there?

Elisa Bass 4L
Posts: 61
Joined: Fri Sep 28, 2018 12:23 am

Re: Molar Mass: E21

Start by calculating the molar mass of the compound. The molar mass will be in grams/mol.

Sofia Ban
Posts: 30
Joined: Fri Sep 28, 2018 12:25 am

Re: Molar Mass: E21

To find the amount (in moles), start by calculating the molar mass of the compound and then divide the given mass by this value. In order to find the number of molecules and formula units, multiply the mole amount by Avogadro's constant.

Shubham Rai 2C
Posts: 64
Joined: Fri Sep 28, 2018 12:27 am

Re: Molar Mass: E21

Yes, first convert all the values to their SI Unit equivalent. Then, find the molar mass of the compound in question using the periodic table. After getting the molar mass, fin the moles of the substance by dividing the amount present by the molar mass of that substance. Finally, to find the number of molecules and/or formula units, multiply the moles of the substance by the Avogadro's number.