What formula do I use to calculate the mass of KCl that is required to make 625 mL of a 0.200 M solution?
Dr Robb the formula you gave me didn't give me the correct answer and I think I did it wrong it is asking for the answer in grams which should be 9.3 grams but I cant get that answer no matter how I work it. Help please
You just didn't use it correctly.
M = moles/L
moles = M x L = 0.200 M x 0.625 L = 0.125 moles.
grams = moles x molar mass
g = 0.125 x 74.55 = 9.3187 grams which rounds to 9.32 grams KCl to three significant figures (which is what you are allowed). .
thank you so much Dr Bob I couldn't figure it out at all.
To calculate the mass of KCl required to make a 0.200 M solution, we can use the formula:
Mass = Concentration (mol/L) x Volume (L) x Molar Mass (g/mol)
In this case, we need to find the mass of KCl, given that the concentration is 0.200 M and the volume is 625 mL (which can be converted to liters by dividing by 1000).
First, let's convert the volume to liters:
625 mL ÷ 1000 = 0.625 L
Now, we need the molar mass of KCl. Potassium (K) has a molar mass of 39.10 g/mol, and chlorine (Cl) has a molar mass of 35.45 g/mol. Adding these two values together, the molar mass of KCl is:
39.10 g/mol + 35.45 g/mol = 74.55 g/mol
Now we can substitute the values into the formula:
Mass = 0.200 mol/L x 0.625 L x 74.55 g/mol
Calculating this equation should give us the correct mass in grams.