[StonerPenguin]

Hello all! I'm new here and I did read the forum rules and it says I'm not allowed to have a question in the topic... But I am allowed to ask questions, right?   Anywho, I already did this problem, I'd just like to double-check my work here because I'm not sure I did it right, and since I'm studying independantly, I'd really appreciate any helpful info on what I did wrong and why it's wrong  

Here's the question(s);
A "To the nearest atomic mass unit, what is the formula mass of aluminum oxide, Al2O3? Show your calculations."

My answer; According to my textbook, the atomic mass of Aluminum is 26.982amu and the atomic mass of Oxygen is 15.999amu.
So, the atomic mass should be (26.982 X 2) + (15.999 X 3) = 101.961amu which to the nearest atomic mass unit is 102amu?

B "To the nearest gram, what is the molar mass of Al2O3?"

My answer; 102 grams per mole, right?

C "How many moles are present in 408 grams of Al2O3? Show your calculations."

My answer; Approximately 4 moles since 408/102 = 4

D "How many molecules are present in 408 grams of Al2O3? Show your calculations."

My Answer; Approximately  4 X 6.02 X 10^23 = 24.08 X 10^23

E "Consider the balanced equation Al2O3 + 3Cu > 2 Al + 3 Cu. If you have 1 mole of Al2O3 and an unlimited amount of Cu, how many moles of Al can you produce?"

My answer; 2 moles, sice 1 mole Al2 > 2 moles Al

F "If you have 408 grams of Al2O3 and an unlimited supply of Cu, how many grams of Al can you produce (round to the nearest gram)? Show your calculations."

My answer; 408 grams of Al2O3 = 4 moles (approx)
Since there's 2 moles of Al per mole of Al2O3, there should be 8 moles of Al in 408 grams/4 moles of Al2O3. There's 26.982 grams of Al per mole so; 8 X 26.982 = 215.856 grams which rounded to the nearest gram is 216 grams.

So... did I do this correctly? Thanks so much for any help in advance  

[JGK]

Seems correct however, I would have put the answer to D as 2.408 X 10²⁴ and not 24.08 X 10²³