Question Video: Determining the Correct Sequence of Steps Needed to Conduct an Experiment Using the Precipitation Method | Nagwa Question Video: Determining the Correct Sequence of Steps Needed to Conduct an Experiment Using the Precipitation Method | Nagwa

Question Video: Determining the Correct Sequence of Steps Needed to Conduct an Experiment Using the Precipitation Method Chemistry • Third Year of Secondary School

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Which of the following choices shows the correct numerical order of the steps of the experiment of quantitative analysis using the precipitation method? 1. Mix the substances together to yield the precipitate. 2. Transfer the precipitate to an ignition crucible and completely ignite. 3. Isolate the precipitate by using ashless filter paper. 4. Weigh the mass of the remaining precipitate. [A] 1, 2, 3, 4 [B] 1, 2, 4, 3 [C] 1, 4, 3, 2 [D] 1, 3, 2, 4 [E] 1, 4, 2, 3

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Video Transcript

Which of the following choices shows the correct numerical order of the steps of the experiment of quantitative analysis using the precipitation method? (1) Mix the substances together to yield the precipitate. (2) Transfer the precipitate to an ignition crucible and completely ignite. (3) Isolate the precipitate by using ashless filter paper. (4) Weigh the mass of the remaining precipitate. (A) 1, 2, 3, 4; (B) 1, 2, 4, 3; (C) 1, 4, 3, 2; (D) 1, 3, 2, 4; (E) 1, 4, 2, 3.

This question is asking us about the steps of a laboratory procedure that would be performed during quantitative chemical analysis using the precipitation method. The type of quantitative analysis that uses a precipitation reaction to determine the mass of an analyte is called precipitation gravimetry. Let’s clear some space to discuss a possible sequence of steps used in this type of experiment.

In a precipitation reaction, a reaction between two soluble substances in solution produces an insoluble solid product called a precipitate. So, the first step in the experiment would be to mix together the soluble substances in the two solutions to form a precipitate. This corresponds to step one in the provided list of steps.

Next, we need to isolate the precipitate from the rest of the solution so that we can eventually determine its mass. The precipitate can be separated from the rest of the solution by using filtration. It’s important that ashless filter paper is used during this step. So, step two of the experiment is to isolate the precipitate by using ashless filter paper.

Now, the problem is that the filter paper and the precipitate are wet. The precipitate needs to be completely dry in order for us to analyze its mass. We can fold the filter paper over the wet precipitate and place it in an ignition crucible, which is typically made of porcelain or metal. This allows us to heat the filter paper strongly enough so that it ignites. At first the paper will dry, but then it will begin to char.

After continuing to heat even more strongly, at some point, all of the paper will have burned. With all of the remnants of the ashless filter paper gone, only the dry precipitate remains in the crucible. So, step three of the experiment is to transfer the precipitate to an ignition crucible and completely ignite.

Now that the precipitate is fully dry, we can find its mass using an analytical balance.

Now let’s bring the answer choices back up on screen to answer the question. Through our discussion, we have determined that the correct numerical order of the steps listed in the problem is 1, 3, 2, 4. Therefore, the correct answer is answer choice (D): 1, 3, 2, 4.

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