How do you calculate the number of moles from volume?

3 Answers
Write your answer here...
Start with a one sentence answer
Then teach the underlying concepts
Don't copy without citing sources
preview
?

Answer

Write a one sentence answer...

Answer:

Explanation

Explain in detail...

Explanation:

I want someone to double check my answer

Describe your changes (optional) 200

395

Answer:

It depends on the substance whose volume you know.

Explanation:

If you have a pure liquid or a solid, you use its density to calculate its mass and then divide the mass by the molar mass.

If you have a solution, you multiply the molarity by the volume in litres.

MOLES FROM VOLUME OF PURE LIQUID OR SOLID

There are two steps:

  1. Multiply the volume by the density to get the mass.
  2. Divide the mass by the molar mass to get the number of moles.

Example

How many moles are in 10.00 mL of acetic anhydride? The molar mass of acetic anhydride is 102.1 g/mol and its density is 1.080 g/mL?

Solution

The formula for density is

#color(blue)(ul(bar(|color(white)(a/a) ρ = m/V color(white)(a/a)|)))" "#

where #ρ# is the density, #m# is the mass, and #V# is the volume of the sample.

We can rearrange the formula to get

#m = V × ρ#

#"mass" = 10.00 color(red)(cancel(color(black)("mL"))) × "1.080 g"/(1 color(red)(cancel(color(black)("mL")))) = "10.80 g"#

#n = 10.80 color(red)(cancel(color(black)("g"))) × "1 mol"/(102.1color(red)(cancel(color(black)("g")))) = "0.1058 mol"#

MOLES FROM VOLUME OF SOLUTION

Molarity is the number of moles of a substance in one litre of solution.

#color(blue)(bar(ul(|color(white)(a/a) M = n/Vcolor(white)(a/a)|)))" "#

where #n# is the number of moles and #V# is the volume in litres.

We can rearrange this equation to get the number of moles:

#n = M × V#

Example

How many moles of #"NaCl"# are contained in 0.300 L of 0.400 mol/L #"NaCl"# solution?

Solution

#n = 0.300 color(red)(cancel(color(black)("L soln"))) × "0.400 mol NaCl"/(1 color(red)(cancel(color(black)("L soln")))) = "0.120 mol NaCl"#

Was this helpful? Let the contributor know!
1500
Write your answer here...
Start with a one sentence answer
Then teach the underlying concepts
Don't copy without citing sources
preview
?

Answer

Write a one sentence answer...

Answer:

Explanation

Explain in detail...

Explanation:

I want someone to double check my answer

Describe your changes (optional) 200

43

At STP one gram mole of an IDEAL gaseous substance occupies 22.7 liters. Hence the if an element is in a gaseous state with volume V liters the number of moles is =V/22.7 approximately. Dimension less this number indicates the chemical mass of any reactant to calculate yields.

Was this helpful? Let the contributor know!
1500
Write your answer here...
Start with a one sentence answer
Then teach the underlying concepts
Don't copy without citing sources
preview
?

Answer

Write a one sentence answer...

Answer:

Explanation

Explain in detail...

Explanation:

I want someone to double check my answer

Describe your changes (optional) 200

22
Jan 28, 2015

Here are a couple of examples of mole-volume conversions.

The first part shows you how to convert from 0.30mol of CO to liters of CO.

The second part shows the conversion from 18.2L Ne to moles of Ne.

The problems were completed assuming both gases are at STP (standard temperature and pressure conditions).


video from: Noel Pauller

Hope this helps.

Was this helpful? Let the contributor know!
1500