Which separation should come first? — questions

1. Describe / Explain

Dry L and M are mixed. Water dissolves L only; paper retains M. Neither reacts with water. L stays unchanged and non-volatile during the teacher-approved water-removal method. Order the actions to collect L and M separately.

Write the number of each step in order.

1. Remove water from the separate filtrate to recover L.
2. Add enough water and stir to dissolve L.
3. Filter to retain M and collect the solution of L.

• First: ______
• Second: ______
• Third: ______

Explain why filtration must come before water removal, following both solids.

Nudge (only if you are stuck): When do L and M take different routes? Which liquid should you remove water from afterwards?

2. Suggest / Describe / Explain

The sample already contains water, fully dissolved N and insoluble O grains. Paper retains O; neither solid reacts with water. An approved method removes water without changing stable, non-volatile N. Plan a sequence to collect both solids separately. Explain their destinations and whether a magnet or another dissolving stage is justified.

First separation — action, products and reason

Recover the other solid — action and reason

Explain why magnetic collection and another dissolving stage are unnecessary

Nudge (only if you are stuck): What is already dissolved? Do the facts name any magnetic component?

3. Explain / Suggest

A wet feed contains water, dissolved X and insoluble Y grains retained by paper. Neither reacts with water. You want only unchanged Y, which decomposes under the proposed heating-to-dryness method. A colleague proposes heating everything first, then filtering the dry material. Assess the plan and suggest a suitable separation. Name both products and state whether recovering X is needed.

Assess heating the whole feed first

Describe the separation needed, its residue and its filtrate

Is recovering X needed for the stated goal? Explain.

Nudge (only if you are stuck): Which product do you actually want? Can filtration collect it now, without a heating step that changes it?

4. Describe / Explain

The filtration log says insoluble D was retained. Dissolved E passed with water. The receiver is labelled ‘D in pure water’. Correct the label, explain why the liquid is filtrate, and identify both contradictions in the old label.

Nudge (only if you are stuck): Which component didn't reach the receiver? Which one means the collected liquid isn't pure water?

5. Suggest / Explain

You want unchanged H and J separated by dissolving and filtering. A dissolves only H but reacts with it. B dissolves only H and reacts with neither solid. C dissolves both without reaction. Handling is approved for this written task, and paper retains undissolved J. Choose a liquid and explain why the other two fail. Don't propose solvent recovery.

Circle one answer.

• A
• B
• C

Justify your candidate and explain why each of the other two fails. No solvent recovery is requested.

Nudge (only if you are stuck): Does a useful solubility difference help if the liquid changes the wanted substance?

6. Suggest / Explain

Use the supplied paper-performance data. Your feed contains fine insoluble grains and salt solution. Choose a paper and describe both products. Explain why neither paper collects dissolved salt as residue.

Paper choice and reason

Residue and filtrate — name their components

Why neither paper recovers dissolved salt

Nudge (only if you are stuck): Which paper retains the fine grains? What does the table separately say about dissolved salt?