Question

How many moles of solute are needed to make 250 mL of a 0.50 M solution of sodium phosphate

Answer 1

0.125 moles of solute

Step-by-step explanation:

The formula for molarity (M) is moles of solute/liters of solution. First, convert 250 mL into liters:

250 mL/1 * 1 L/1000 mL = 0.25 L.

Then, plug in the values of m/L = M

m/0.25 = 0.5

Solve for moles (m). You would multiply 0.5 by 0.25.

m = 0.125

Lastly, if you'd like to check it and see if it's correct, do 0.125/0.25, and you should get 0.5 M.

Answer 2

`\boxed {\boxed {\sf 0.125 \ mol }}`

Step-by-step explanation:

Molarity is a measure of concentration. It is the moles of solute per liters of solution.

`molarity = ( moles \ of \ solute)/( liters \ of \ solution)`

We know the solution has a molarity of 0.5 M or moles per liter. There are 250 milliliters of solution. First, we need to convert to liters. 1 liter is equal to 1000 milliliters.

• 
  `\frac {1 \ L}{ 1000 \ mL}`

• 
  `250 \ mL *\frac {1 \ L}{ 1000 \ mL}`

• 
  `\frac {250 }{ 1000 } \ L = 0.25 \ L`

Now we can substitute the values we know into the formula.

• molarity= 0.5 mol/L
• liters of solution = 0.25 L
• moles of solute=x (unknown)

`0.5 \ mol/L= ( x)/(0.25 \ L)`

Since we are solving for the moles of solute, we need to isolate the variable x. It is being divided by 0.25 L. The inverse of division is multiplication. Multiply both sides by 0.25 L.

`0.25 \ L *0.5 \ mol/L= ( x)/(0.25 \ L)*0.25 \ L`

`0.25 \ L * 0.5 \ mol/L =x`

`0.25 * 0.5 \ mol=x`

`0.125 \ mol =x`

0.125 moles of sodium phosphate are needed to make 250 mL of a 0.50 M solution.