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How many grams of ammonium sulfate are needed to make a 0.25 L solution at a...

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chris134 | Student, College Freshman | eNoter

Posted April 1, 2011 at 8:03 AM via web

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How many grams of ammonium sulfate are needed to make a 0.25 L solution at a concentration of 6 M?

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted April 1, 2011 at 11:53 AM (Answer #1)

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The concentration of a solution can be expressed in many way, one of them is molarity or the molar concentration. If a solution has a molarity of one, it has one mole of the solute in every liter of the solution.

Here we need to find the number of grams of ammonium sulfate needed to make 0.25 L of solution with a molarity of 6 M.

A solution with a molarity of 6 M has 6 moles of the solute per liter. 0.25 L of a solution with a molarity of 6M has 6*0.25 = 1.5 moles of the solute.

The molar mass of ammonium sulfate is 132.14 g/mole. The mass of 1.5 moles is 132.14*1.5 = 198.21 g.

Therefore 198.12 g of ammonium sulfate are required to make 0.25 L of a solution with a concentration of 6M.

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donleonardo | Honors

Posted June 22, 2011 at 2:28 PM (Answer #2)

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Moles = mass of solute/ gram molecular mass. Solute is the 'stuff being disolved. Solution is a homogeneous mixture of a solute in a solven. G.M.M. is gram molecular mass

.                                    moles of solute

Molarity is defined as: ___________________________________

.                                                 liters of solution

.                   [g (NH4)2SO4/G.M.M]

6 M = ______________________________

.                     L (NH4)2SO4(aq)

.             ? g / 132g/mol

6 M =  __________________

.                 0.25 L

 

g (NH4)2SO4 = 6 mol/L * 0.25 L * 132 g/mol = 198 g(NH4)2SO4

Since 6M is only 1 significant figure the answer to 1 significant figure would be 200 g (NH4)2SO4. 6.0M solution would also use 200 (with the bold numbers representing the significant figures)

If the solution were 6.00M (3 sig figs) then you would need 198 g(NH4)2SO4

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