Question

What is the molarity of 225 grams of Cu(NO2)2 in a total volume of 2.59 L?

Answer 1

Answer:

The molarity is 0.56$\frac{moles}{L}$

Explanation:

In a mixture, the chemical present in the greatest amount is called a solvent, while the other components are called solutes. Then, the molarity or molar concentration is the number of moles of solute per liter of solution.

In other words, molarity is the number of moles of solute that are dissolved in a given volume.

The Molarity of a solution is determined by:

$Molarity (M)=\frac{number of moles of solute}{Volume}$

Molarity is expressed in units ($\frac{moles}{liter}$).

Then you must know the number of moles of Cu(NO₂)₂. For that it is necessary to know the molar mass. Being:

• Cu: 63.54 g/mol
• N: 14 g/mol
• O: 16 g/mol

the molar mass of Cu(NO₂)₂ is:

Cu(NO₂)₂= 63.54 g/mol + 2*(14 g/mol + 2* 16 g/mol)= 155.54 g/mol

Now the following rule of three applies: if 155.54 g are in 1 mole of the compound, 225 g in how many moles are they?

$moles=\frac{225 g*1 mole}{155.54 g}$

moles= 1.45

So you know:

• number of moles of solute= 1.45 moles
• volume=2.59 L

Replacing in the definition of molarity:

$Molarity=\frac{1.45 moles}{2.59 L}$

Molarity= 0.56$\frac{moles}{L}$

The molarity is 0.56$\frac{moles}{L}$