A sample of Magnesium Oxide was found to be contaminated with the sodium chloride. Magnesium oxide is not very soluble in water but can be dissolved in an excess of the standardisted HCl

In order to determine the purity of the magnesium oxide, 3.86g of the sample was dissolved in 500ml of Hcl and then 50ml of the resulting solution was titrated against the NaOH solution of known concentration. The average titration volume was found to be 10.4ml.

Calculate the percentage of magnesium oxide in the concentration sample.

To determine the percentage of magnesium oxide (MgO) in your sample, we need to follow a series of logical steps involving stoichiometry and the principles of acid-base titration. Let's break this down step by step.

Understanding the Reaction

When magnesium oxide reacts with hydrochloric acid (HCl), it forms magnesium chloride (MgCl₂) and water. The balanced chemical equation for this reaction is:

• MgO + 2 HCl → MgCl₂ + H₂O

This indicates that one mole of MgO reacts with two moles of HCl. In the titration, the excess HCl that remains after reacting with MgO is neutralized by sodium hydroxide (NaOH). The balanced equation for the titration reaction is:

• HCl + NaOH → NaCl + H₂O

Calculating Moles of NaOH Used

First, we need to find out how many moles of NaOH were used in the titration. The average volume of NaOH used was 10.4 mL, which we convert to liters:

• 10.4 mL = 0.0104 L

Assuming the concentration of the NaOH solution is known (let's denote it as C NaOH in moles per liter), the number of moles of NaOH used can be calculated using the formula:

• moles of NaOH = concentration (C) × volume (L)

Finding Moles of HCl Neutralized

From the stoichiometry of the reaction, we know that one mole of NaOH neutralizes one mole of HCl. Therefore, the moles of HCl that were neutralized is equal to the moles of NaOH used.

Determining Moles of HCl Initially Present

Next, we need to calculate the total moles of HCl that were initially present in the 500 mL solution. The concentration of HCl can be calculated based on the amount of HCl that reacted with MgO. Since we know that 2 moles of HCl react with 1 mole of MgO, we can find the moles of HCl that reacted with the MgO:

• moles of HCl reacted = moles of NaOH used

Calculating Moles of MgO

Using the stoichiometry from the first reaction, we can find the moles of MgO that were present in the original sample:

• moles of MgO = (moles of HCl reacted) / 2

Finding the Mass of MgO

Now, we can calculate the mass of MgO in the sample using its molar mass. The molar mass of MgO is approximately 40.3 g/mol (for Mg) + 16.0 g/mol (for O) = 56.3 g/mol. Thus:

• mass of MgO = moles of MgO × molar mass of MgO

Calculating the Percentage Purity

Finally, to find the percentage of magnesium oxide in the original sample, we can use the formula:

• percentage of MgO = (mass of MgO / mass of sample) × 100

Now, let's plug in the numbers. If we assume the concentration of NaOH is, for example, 0.1 M, we can calculate:

• moles of NaOH = 0.1 mol/L × 0.0104 L = 0.00104 moles
• moles of HCl reacted = 0.00104 moles
• moles of MgO = 0.00104 moles / 2 = 0.00052 moles
• mass of MgO = 0.00052 moles × 56.3 g/mol = 0.0293 g
• percentage of MgO = (0.0293 g / 3.86 g) × 100 ≈ 0.76%

Thus, the percentage of magnesium oxide in your sample can be calculated based on the actual concentration of NaOH used in your titration. Just replace the assumed concentration with the actual value to get your final result.