- Units & Notation
- Moles per litre
- Grams per litre
- Percent solutions
- Parts per million
- Practice problems
Practice problems
Activity 3
How many grams of Sodium Chloride should be added to 2L of buffer to make a 4mM solution?
Try to attempt this problem yourself. Type-in your answer (digits only) in the text box given below and then check your answer by clicking the 'Check Answer' button.
Volume of solution is 2 litres. Concentration/molarity of solution is 4mM. Notice here that the concentration is in moles but we are asked for the amount Sodium Chloride in grams, so we will find the amount of Sodium Chloride in moles and then convert it into grams. The amount of Sodium Chloride in moles can be calculated by placing in the formula for concentration the values provided in the problem statement. Before doing so, the value of molarity needs to be in moles. Using the conversion:
Placing the values in the formula:
we get:
From the above equation, the amount of Sodium Chloride in moles is 0.008 M.
M r for Sodium Chloride is approximately 58.5 and remembering the formula:
we get:
From the above equation the amount of Sodium Chloride in grams is 0.468g.
If you have got the answer right then try Activity 4, or else the video below shows a detailed step by step approach to solve the above problem.
This video contains sound.
