Question

A student calculated the theoretical yield of barium sulfate in a precipitation experiment to be \(1.352 \mathrm{g}\) When she filtered, dried, and weighed her precipitate, however, her yield was only \(1.279 \mathrm{g}\). Calculate the student's percent yield.

Short answer

The student's percent yield for the precipitation experiment is 94.59%.

Step-by-step solution

Identify the Given Values

Actual yield: 1.279 g Theoretical yield: 1.352 g The formula for percent yield is: Percent Yield = (Actual Yield / Theoretical Yield) × 100

Substitute the Given Values into the Formula

Percent Yield = (1.279 g / 1.352 g) × 100

Perform the Calculation

Divide 1.279 g by 1.352 g: \(1.279\div 1.352 = 0.9459\) Now multiply the result by 100 to find the percent yield: \(0.9459 \times 100 = 94.59\)

State the Final Result

The student's percent yield for the precipitation experiment is 94.59%.

Key concepts

Theoretical Yield

In chemistry, the theoretical yield is a term used to describe the maximum amount of product that could be generated from a chemical reaction, under perfect conditions. It is a purely calculated value, based on stoichiometric calculations involving the balanced chemical equation, which outlines the ratio in which reactants combine to form products.

The theoretical yield assumes no loss of material and perfect efficiency, which in reality is seldom achieved due to side reactions, incomplete reactions, and other practical limitations. To calculate the theoretical yield, one must first identify the limiting reagent in the reaction – the reactant that will be entirely consumed first, limiting the amount of product formed. From there, using the molar mass of the reactants and products, we can determine the expected amount of product in grams or moles.

Actual Yield

Contrary to the theoretical yield, the actual yield is the actual amount of product obtained from a chemical reaction. It is measured directly from the experimental procedure. The actual yield is almost always less than the theoretical yield due to the various inefficiencies in the experimental process.

Factors such as incomplete reactions, competing side reactions, loss of product during transfer, purification, and measurement, and even measurement errors can all contribute to a lower actual yield. Calculating the actual yield is straightforward: after conducting the experiment, the product is collected and measured. Understanding the difference between actual and theoretical yields is essential in evaluating the efficiency of chemical processes and in scaling up reactions for industrial applications.

Precipitation Reaction

A precipitation reaction is a type of chemical reaction where a solid, known as a precipitate, forms and separates from a solution. It occurs when two soluble reactants produce an insoluble product that settles out of the solution.

These reactions are commonly observed in the formation of ionic compounds when a cation from one reactant combines with an anion from another, leading to the formation of a solid. Precipitation reactions are frequently used in chemical analysis, to isolate products in a pure form, and in various industries such as wastewater treatment. The solid precipitate that forms can be collected by filtration, as seen in the example exercise, where barium sulfate precipitates and is collected by the student.