Hi Avery,
Concentration is typically measured in Molarity (M), which is equal to moles/Liter of solution (mol/L). To determine the concentration of your NaOH solution, you will need to convert the 10g into moles of NaOH and change the 150 mL to 0.15 L. To convert grams into moles, use the molar mass of NaOH (40 g/mol, which can be found by using your periodic table to add up the molar mass of each element). This means that 1 mole of NaOH will weigh 40 grams. Since you only have 10g, you should expect your answer to be less than 1 mole. Set it up so that your grams units will cancel, leaving your answer in moles.
10 g NaOH x 1 mol NaOH = 0.25 moles NaOH
40 g NaOH
Now, determine the concentration by dividing moles per Liters of solution
0.25 mol = 1.67 M (or mol/L)
0.15 L
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For the second question, you are given the concentration in Molarity (mol/Liter) and asked to calculate how many moles were needed to make that amount of solution. You can use the Molarity calculation and plug in the info already given to you. Don't forget to convert your 65 mL to 0.065 L
Molarity (M) = moles (mol)
Liter of solution (L)
1.5 M = x mol
0.065 L
Solve for x by multiplying both sides of the equation by 0.065 L
1.5M(mol/L) • 0.065 L = x mol
x = 0.0975 moles
