0.05 mole of LiAIH, in ether solution was placed in a flask containing 74g (1 mole) of t-butyl alcohol. The product LiAIHC_l2H₂₇0₃ weighed 12.7 g. If Li atoms are conserved, the percentage yield is : (Li = 7, Al = 27, H = 1,0= 12,0= 16).

To determine the percentage yield of the reaction involving lithium aluminum hydride (LiAlH4) and t-butyl alcohol (t-BuOH), we’ll need to follow a few steps. We will calculate the theoretical yield based on the number of moles of reactants and then compare it with the actual yield provided.

Step 1: Understanding the Reaction

In this reaction, LiAlH4 reacts with t-butyl alcohol to form LiAlHCl2H2O and other by-products. The balanced equation for this reaction would typically involve the conversion of the lithium aluminum hydride and t-butyl alcohol into the final product, although the complete reaction details aren't provided. However, we can still calculate based on the information given.

Step 2: Moles of Reactants

We start by noting the moles of LiAlH4. We have:

• 0.05 moles of LiAlH4
• 1 mole of t-butyl alcohol (74 g)

This indicates we have a sufficient amount of t-butyl alcohol since it’s in excess compared to LiAlH4, which will limit the reaction based on the amount of LiAlH4 present.

Step 3: Molecular Weights

To calculate the theoretical yield, we need to know the molecular weight of the product, LiAlHCl2H2O. Let’s calculate that:

• Li: 7 g/mol
• Al: 27 g/mol
• H: 1 g/mol (4 H in total: 3 from LiAlH4, 1 from HCl)
• Cl: 35.5 g/mol (2 Cl from 2 HCl)
• O: 16 g/mol (2 from 2 H2O)

Thus, the molecular weight of LiAlHCl2H2O is:

7 (Li) + 27 (Al) + 4 (H) + 71 (Cl) + 18 (O) = 127 g/mol

Step 4: Theoretical Yield Calculation

With 0.05 moles of LiAlH4, we can calculate the theoretical yield of LiAlHCl2H2O:

Theoretical yield = moles × molar mass

Theoretical yield = 0.05 moles × 127 g/mol = 6.35 g

Step 5: Actual Yield and Percentage Yield Calculation

The actual yield of the product is given as 12.7 g. The percentage yield can now be calculated using the formula:

Percentage Yield = (Actual Yield / Theoretical Yield) × 100

Plugging in the values:

Percentage Yield = (12.7 g / 6.35 g) × 100 ≈ 200%

Final Thoughts

In this case, a percentage yield over 100% suggests that either the theoretical yield calculated may not account for all factors, or there might be other components contributing to the mass of the product. It is essential to ensure that all reactants are accurately accounted for and that the product's weight solely corresponds to the desired compound, as impurities can significantly affect such calculations.