Calculate the concentration of a standard solution of hydrated oxalic acid (H2C2O4·2H2O) prepared by dissolving 25.21g of hydrated oxalic acid in 250.0mL of deionised water.
The correct answer and explanation is :
Calculation of the Concentration of Hydrated Oxalic Acid Solution
To calculate the concentration of the standard solution of hydrated oxalic acid ((\text{H}_2\text{C}_2\text{O}_4 \cdot 2\text{H}_2\text{O})), we follow these steps:
Step 1: Determine the Molar Mass of Hydrated Oxalic Acid
The molar masses of the constituent elements are:
- Hydrogen (H) = (1.008 \times 4 = 4.032) g/mol
- Carbon (C) = (12.01 \times 2 = 24.02) g/mol
- Oxygen (O) = (16.00 \times 6 = 96.00) g/mol
- Water of hydration ((2\text{H}_2\text{O})) = (18.02 \times 2 = 36.04) g/mol
Total molar mass of (\text{H}_2\text{C}_2\text{O}_4 \cdot 2\text{H}_2\text{O}):
[
4.032 + 24.02 + 96.00 + 36.04 = 126.09 \text{ g/mol}
]
Step 2: Calculate the Number of Moles of Hydrated Oxalic Acid
Using the given mass of 25.21 g:
[
\text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{25.21}{126.09} = 0.2 \text{ mol}
]
Step 3: Calculate the Molar Concentration
Concentration ((C)) is given by:
[
C = \frac{\text{Moles of solute}}{\text{Volume of solution in liters}}
]
Since the solution volume is 250.0 mL = 0.2500 L,
[
C = \frac{0.2}{0.2500} = 0.800 \text{ mol/L}
]
Explanation
The concentration of a solution refers to the amount of solute (in moles) dissolved in a given volume of solvent (in liters). In this case, the solute is hydrated oxalic acid, and the solvent is deionized water.
We determined the concentration by:
- Finding the molar mass of hydrated oxalic acid to understand how many grams constitute one mole.
- Calculating the number of moles in the given mass of 25.21 g.
- Dividing the moles by the solution volume to obtain the molarity.
The result, 0.800 mol/L (M), means there are 0.800 moles of hydrated oxalic acid per liter of solution. This standard solution can now be used in titrations or other quantitative chemical analyses.