Calculate the mass in grams of sodium bromide, NaBr, are needed to prepare 250.0 mL of a solution of sodium bromide that is 3.50% (m/v).
3.50% m/v means 3.50 grams NaBr/100 mL soln. You can do this one of two ways (They really are the same but the look is different.)
3.50 x (250/100) = ??
or
(Xg/250 mL)*100 = 3.50 and solve for X.
To calculate the mass of sodium bromide (NaBr) needed to prepare the solution, we need to use the formula:
Mass = Volume x Concentration
First, convert the given volume of the solution from milliliters (mL) to liters (L) since the concentration is usually expressed in grams per liter (g/L).
Given:
Volume = 250.0 mL
Converting the volume to liters:
Volume (in L) = 250.0 mL * (1 L / 1000 mL) = 0.250 L
Next, calculate the mass using the concentration:
Given:
Concentration = 3.50% (m/v) = 3.50 g/100 mL
Converting the concentration to grams per liter (g/L):
Concentration (in g/L) = (3.50 g/100 mL) * (10 g/1 mL) = 35.0 g/L
Now, we can calculate the mass:
Mass = Volume x Concentration
Mass = 0.250 L * 35.0 g/L
Mass = 8.75 grams
Therefore, 8.75 grams of sodium bromide (NaBr) are needed to prepare 250.0 mL of a solution that is 3.50% (m/v).