Question

a laboratory procedure calls for making 510.0 mL of a 1.6 M KNO3 solution. How much KNO3 in grams is needed

Answer 1

82.416 g of KNO ₃ is needed to produce 510.0 mL of a 1.6 M KNO ₃ solution.

Step-by-step explanation:

Since molarity is the number of moles of solute that are dissolved in a given volume, calculated by dividing the moles of solute by the volume of the solution, the following rule of three can be applied: if in 1 L (1,000 mL) of KNO₃ there are 1.6 moles of the compound present, in 510 mL how many moles will there be?

`moles=(510 mL*1.6 moles)/(1000 mL)`

moles= 0.816

Being the molar mass of the elements:

• K: 39 g/mole
• N: 14 g/mole
• O: 16 g/mole

So the molar mass of the compound KNO₃ is:

KNO₃= 39 g/mole + 14 g/mole + 3*16 g/mole= 101 g/mole

Now I can apply the following rule of three: if in 1 mole of KNO₃ there are 101 g, in 0.816 moles how much mass is there?

`mass=(0.816 moles*101 grams)/(1 mole)`

mass= 82.416 grams

82.416 g of KNO ₃ is needed to produce 510.0 mL of a 1.6 M KNO ₃ solution.