= 78 g of NaOH
Concentration = Moles of solute/Volume of solution
Thus;
Moles of the solute = Volume × Concentration
= 7.80 Moles/L × 0.250 L
= 1.95 moles
But; 1 mole of NaOH = 40.0 g
Thus;
Mass of NaOH = moles × molar mass
= 1.95 moles × 40 g/mole
= 78 g of NaOH
78 g of NaOH
Given:
Question:
How many grams of sodium hydroxide are needed to make 250 ml of a 7.80 M solution?
The Process:
Step-1
Let us prepare the relative molecular mass (Mr) of NaOH.
Step-2
The concentration of the solution is a mole of solute divided by 1 liter of solution.
[tex]\boxed{ \ M = \frac{n}{V} \ }[/tex] (Remember V in liters here)
We know that mole is mass divided by molecular mass.
[tex]\boxed{ \ n = \frac{mass}{Mr} \ }[/tex]
The relationship between concentration (M), mass, relative molecular mass (Mr), and volume of solution in ml (V) is as follows:
[tex]\boxed{ \ M = \frac{mass}{Mr} \times \frac{1,000}{V} \ }[/tex] (Remember V in ml here)
Substitute all known data into the equation.
[tex]\boxed{ \ 7.80 = \frac{mass}{40} \times \frac{1,000}{250} \ }[/tex]
[tex]\boxed{ \ 7.80 = \frac{mass}{40} \times 4 \ }[/tex]
[tex]\boxed{ \ 7.80 = \frac{mass}{10} \ }[/tex]
Mass = 7.80 x 10
Mass = 78
Thus, the number of grams of sodium hydroxide are needed to make 250 ml of a 7.80 M solution is 78 grams.
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Notes:
The concentration of the solution, especially in this case molarity, represents one significant data. Among them play a role in
