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Homework Help: What is the mass of one mole of aluminum?

  1. Feb 7, 2006 #1
    I have almost my entire worksheet done but I wanted to check my answers and get some help with the final question.:smile:

    What is the mass of one mole of aluminum?
    The mass of one mole of aluminum is 26.981 grams.

    What is the mass of one mole of hydrogen?

    1.008 g

    What is the mass of one mole of carbon dioxide, CO2?

    4.4009 x 10^1 g

    What is the mass of one mole of sulfuric acid?

    9.8079 x 10^1 g

    How many moles in 3.00 g H2SO4?

    .030 mol

    How many moles in 12.0 g CH4?

    .748 mol

    How many moles in 3.40 x 10^1g CaO?

    .606 mol

    How many moles in 13.4 g SO2?

    .21mol

    What is the mass of 0.369 mol N2?

    10.337 g

    What is the mass of 10.0 mol Ca(NO3)2?

    1641 g

    What is the mass of 1.94 x 10^-3 mol C6H12O6?

    .340 g

    What is the mass of 0.0112 KCl ?

    .840 g

    How many particles in 25.9 mol Fe ?

    1.56 x 10^25

    How many particles in 0.30 mol NaCl ?

    1.8 x 10^23

    How many moles in 4.7 x 10^24 atoms Cu?

    7.8


    This is the one I need help with:

    How many moles in 8.30 x 10^25 molecules H2O?

    138
    245
    213
    156


    I hope I at least did the other ones correctly.:rofl:
     
  2. jcsd
  3. Feb 7, 2006 #2
    Hi,

    I saw a few of the first ones and they seemed right... sry, kind of lazy to check all of them.

    for the last one


    1 mole = 6.022*10^23 molecules ... in other words:

    ___1mole________________ = ___x-moles_____
    6.022*10^23molecules_____8.30 x 10^25molecules


    \

    now solve for x just by multiplying 8.30*10^25
    which gives you 137.8279641 moles.
    Now, if you count sig. digits that would be 138 moles.
     
    Last edited: Feb 8, 2006
  4. Feb 7, 2006 #3
    I don't blame ya, it's a wonder that I did them all myself.:rofl:

    How are you getting that? I'm a bit confused...I'm assuming, hopefully correctly, that you meant to put the 8.30 x 10^25 on the top, not the bottom? Otherwise, I'm lost.:tongue:
     
  5. Feb 7, 2006 #4
    Its an equation. when you multiply 8.30*10^25 on both sides, the 8.30*10^25 on the right side cancels out and you put it on the left side too ( on top of the equation) then just divide, and as you see, molecules cancel out, leaving you with just moles.

    Remember you are solving for the variable "x-moles"
     
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