Question
An aqueous KNO3 solution is made using 77.8 g of KNO3 diluted to a total solution volume of 2.04 L. Calculate the molarity of the solution. (assume a density of 1.05 g/ml for the solution.)
Final Answer
The molarity of the aqueous KNO₃ solution is approximately 0.377 M.
Explanation
| Data: Revealed information |
| 1. Mass of KNO₃ (potassium nitrate) = 77.8 g 2. Total solution volume = 2.04 L 3. Density of the solution = 1.05 g/ml |
| Unknown: What we need to find Molarity of the solution |
| Formula: The equation we need to apply and solve the problem We need to remember that Molarity (M) is defined as the number of moles of solute per litre of solution. Thus, we need to use: Molarity (M) = Moles of a solute / Litres of solution |
| SI unit: The unit we need to use for our last answer The si unit of molarity is mol/L which is also known as Molar and the symbol is written as M |
Solution:
| Step 1: Calculate the moles of KNO₃. |
| Moles of KNO₃ = Mass / Molar mass We can now calculate the molar mass of KNO₃ by adding the atomic masses of potassium (K), nitrogen (N), and three oxygen (O) atoms: Molar mass of KNO₃ = [39.10 + 14.01 + (3 x 16.00)]g/mol We will now have Molar mass of KNO₃ = (39.10 + 14.01 + 48.00) g/mol = 101.11 g/mol Thus, Moles of KNO₃ = (77.8 g) / (101.11 g/mol) The above expression will now give us: Moles of KNO₃ = 0.770 mol |
| Step 2: Calculate the molarity (M). |
| Molarity (M) = moles of solute / liters of solution Hence, Molarity (M) = 0.770 mol / 2.04 L Our final answer will now become: Molarity (M) = 0.377 M |
Therefore, the molarity of the aqueous KNO₃ solution is approximately 0.377 M.
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