Taking into account the definition of molarity, 4.08 grams of ammonium sulfide are present in 3.00 L of a 0.0200 M solution.
<h3>Definition of molarity</h3>
Molar concentration or molarity is a measure of the concentration of a solute in a solution and indicates the number of moles of solute that are dissolved in a given volume.
The molarity of a solution is calculated by dividing the moles of solute by the volume of the solution:

Molarity is expressed in units
.
<h3>Mass of ammonium sulfide</h3>
In this case, you know:
- Molarity: 0.0200 M
- number of moles: ?
- volume: 3 L
Replacing in the definition of molarity:

Solving:
0.0200
× 3 L= number of moles
<u><em>0.06 moles= number of moles</em></u>
On the other side, the molar mass is the amount of mass that a substance contains in one mole. In this case, the molar mass of ammonium sulfide is 68 g/mole.
Then, the amount of mass contained in 0.06 moles is calculated as:
0.06 moles×
= <u><em>4.08 grams</em></u>
Finally, 4.08 grams of ammonium sulfide are present in 3.00 L of a 0.0200 M solution.
Learn more about
molarity:
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molar mass:
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