Assume you poured 5.00 g of KOH in 250 mL of pure water. What is the molarity of the solution you made?
1 mole of KOH=56.11g
and
250mL=0.250L
Solve for moles:
5.00g*(1 mole/56.11g)= moles of KOH
Molarity=moles/volume (L)
To find the molarity of a solution, you need to know the amount of solute (in moles) and the volume of the solution (in liters). In this case, you have been given the mass of the solute (5.00 g) and the volume of the solution (250 mL).
To determine the amount of solute in moles, you need to use the molar mass of KOH. The molar mass of KOH is calculated by adding up the atomic masses of each element in the compound: potassium (K), oxygen (O), and hydrogen (H).
The atomic mass of potassium (K) is 39.10 g/mol, oxygen (O) is 16.00 g/mol, and hydrogen (H) is 1.01 g/mol. Adding them up gives a molar mass of 39.10 + 16.00 + 1.01 (from hydrogen) = 56.11 g/mol.
To convert the mass of KOH to moles, divide the given mass (5.00 g) by the molar mass (56.11 g/mol):
moles of KOH = 5.00 g / 56.11 g/mol
Now, you need to convert the volume of the solution from milliliters (mL) to liters (L). There are 1000 mL in 1 L, so divide the given volume (250 mL) by 1000:
volume of solution = 250 mL / 1000 mL/L = 0.250 L
Now that you have the amount of solute in moles (moles of KOH) and the volume of the solution in liters (volume of solution), you can calculate the molarity of the solution using the formula:
Molarity (M) = moles of solute / volume of solution (in liters)
Molarity of the solution = moles of KOH / volume of solution
Substituting the calculated values:
Molarity of the solution = (5.00 g / 56.11 g/mol) / 0.250 L
Calculating further:
Molarity of the solution ≈ 0.178 M
So, the molarity of the solution you made is approximately 0.178 M.