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Home Q & A Board Science-Related Homework Help Chemistry (Moderator: Laser_3)
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poshmom poshmom
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12 years ago
I figured out all the others but Im stuck on these four and none of the examples in my book are similar.  The examples are always solving for something else.  HELP!

1-How many mols of NaCl are in 750mL of a 1.5 M NaCl solution?


2-How many grams of Methanol CH3OH; MM=32g/mol) must be added to a 500 mL of water to prepare a solution that is 15%(m/v) CH3OH?  What is the Molarity of this solution (grams solute/mL of solution)x100; M=mols solute/L of solution)?

3-Which would have a bigger impact on the vapor pressure of a solution, 1 mol of C6H12O12 or 1 mol of Na3PO4? Why?

4-Consider the following chemical equation for the combustion of butane (C4H10):

2C4H10(l) + 13O2(g) > 8CO2(g) + 10H2O(g)

How many grams of water will be produced from the combustion of 50.0 g of butane (MM of butane = 58.0g/mol; H2O = 18g/mol)?
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wrote...
#1
12 years ago
Quote
1-How many mols of NaCl are in 750mL of a 1.5 M NaCl solution?

So you have 750 mL and 1.5 M.

1.5 M is mol/L

So, convert 750 mL into L Rightwards Arrow 0.750 L

then, multiple 0.750 L by 1.5. This will give you the moles in the solution. Thinking Face
Biology!
poshmom Author
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#2
12 years ago
Great, thanks.  Any help on the others?
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#3
On Hiatus
12 years ago
4.

First, we calculate the moles of butane:

50.0 g of butane x 1 mole of butane/58.0 g of butane = 0.862 moles

From the moles of butane, we calculate the moles of water from the balanced chemical equation:

0.862 moles of butane x 10 moles of water/2 moles of butane = 4.31 moles

From the moles of water, we calcuate the mass of water:

4.31 moles of water x 18.02 g of water/1 mole of water = 77.67 g

Hope this helps!  Smiling Face with Open Mouth
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#4
12 years ago
Quote from: poshmom (12 years ago)
2-How many grams of Methanol CH3OH; MM=32g/mol) must be added to a 500 mL of water to prepare a solution that is 15%(m/v) CH3OH?  What is the Molarity of this solution (grams solute/mL of solution)x100; M=mols solute/L of solution)?

3-Which would have a bigger impact on the vapor pressure of a solution, 1 mol of C6H12O12 or 1 mol of Na3PO4? Why?

Omgosh! I need these too, I don't understand Sad Dummy
poshmom Author
wrote...
#5
12 years ago
Help Im stuck on this last one and I have to mail it in an hour.  Its #2 on Methanol
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