Calculate the number of molecules of water of crystallization in oxalic acid crystals H2C2O4.nH20 that 5g of the crystals were made upto 250cm³ of the solution.25.0cm³ of the solution required 15.9cm³ of 0.5M sodium hydroxide to neutralize it
To calculate the number of molecules of water of crystallization in oxalic acid crystals, we first need to determine the molar mass of the oxalic acid.
The molecular formula of oxalic acid is H2C2O4.
The molar mass of hydrogen (H) is approximately 1 g/mol, the molar mass of carbon (C) is approximately 12 g/mol, and the molar mass of oxygen (O) is approximately 16 g/mol.
Therefore, the molar mass of H2C2O4 is:
2(1 g/mol) + 2(12 g/mol) + 4(16 g/mol) = 126 g/mol
Next, we need to determine the number of moles of oxalic acid in the 5 g of crystals.
Number of moles = mass / molar mass
Number of moles = 5 g / 126 g/mol ≈ 0.0397 mol
Now, we can use the balanced chemical equation to determine the number of moles of sodium hydroxide (NaOH) required to neutralize the oxalic acid.
The balanced chemical equation is:
H2C2O4 + 2NaOH -> 2H2O + Na2C2O4
According to the equation, 1 mole of H2C2O4 reacts with 2 moles of NaOH.
Therefore, the number of moles of NaOH required to neutralize the oxalic acid can be found using the equation:
Number of moles of NaOH = number of moles of H2C2O4 / 2
Number of moles of NaOH = 0.0397 mol / 2 ≈ 0.0199 mol
From the given information, we know that 25.0 cm³ of the solution required 15.9 cm³ of 0.5 M NaOH to neutralize it.
Using the equation:
Number of moles = concentration × volume (in liters),
We can determine the number of moles of NaOH in 15.9 cm³ of 0.5 M solution:
Number of moles of NaOH = 0.5 mol/L × (15.9 cm³ / 1000 cm³/L) = 0.00795 mol
Now, we can use the ratio of the number of moles of NaOH required to neutralize oxalic acid to find the number of moles of oxalic acid:
0.0199 mol NaOH correspond to 0.0397 mol H2C2O4
So, if 0.0199 mol NaOH are required, then:
0.00795 mol NaOH correspond to (0.0397 mol H2C2O4) × (0.00795 mol NaOH / 0.0199 mol NaOH) ≈ 0.0158 mol H2C2O4
Finally, we can calculate the number of molecules of water of crystallization (nH2O) by comparing the number of moles of oxalic acid (H2C2O4) to the number of moles of water (H2O) using the ratio in the molecular formula.
The molecular formula of oxalic acid crystals is H2C2O4.nH2O, which suggests that for each mole of H2C2O4, there are n moles of H2O.
From the previous calculation, we found that 0.0158 mol H2C2O4 were present.
Since H2C2O4 has no water of crystallization, n = 0.
Therefore, the number of molecules of water of crystallization in oxalic acid crystals H2C2O4.nH2O is 0.