Design a separation and account for every fraction

Choose a process for a difference in properties

Separation works when components respond differently to a process. Here A can dissolve in water while B cannot, and the ideal filter retains undissolved solids while the liquid and dissolved A pass. Filtration does not remove this dissolved A merely because A was originally supplied as a solid. The liquid that passes through is the filtrate; the retained material is the residue.

The flow diagram has branches because filtration produces two fractions. Read one stage at a time. Do not add an intermediate filtrate mass to the later products made from that same filtrate: that counts the same matter twice.

Follow the default mixture

Start with 25 g A, 10 g B and 100 g water: 135 g total. At the stipulated capacity, 20 g A dissolve and 5 g remain solid. The filter retains 10 g B plus 5 g A, totaling 15 g. The filtrate contains 20 g A plus 100 g water, totaling 120 g. The first balance is 135 = 15 + 120.

The model then evaporates all filtrate water without losing or decomposing A. It leaves 20 g A in the product fraction and transfers 100 g water to the surroundings. The final balance is 135 = 15 g filter residue + 20 g recovered A + 100 g water vapor. Reduced mass in the original vessel is not destruction of matter; the boundary must include what left.

Evaporation alone does not collect purified liquid water. Recovering the solvent would require an additional condensation and collection process, with its own transfer and purity evidence. That process is not included in this lab.

Recovery and purity are different claims

Recovery into the selected A product is recovered A divided by initial A. Here it is 20/25 = 0.80, or 80%. All A still exists somewhere in the model, yet only 80% reached the selected product fraction. The remaining 20% is mixed with B in the residue.

If the initial A amount is zero, an A recovery percentage is undefined: its denominator is zero. The app reports that rather than awarding 100% recovery for collecting nothing. The fixed 10 g of B and the supplied water still require accounting.

Purity describes composition of a fraction, not how much of the desired component was recovered. In this ideal model the dry A product contains only A. In real work, a plausible product mass alone cannot establish purity: retained solvent, another dissolved substance or a transformation product could contribute mass. A residue larger than 10 g is not automatically extra B.

Repair an incomplete separation

Keep initial A at 25 g and increase water to 200 g. Capacity becomes 40 g A, so all 25 g dissolve. The filter now retains only 10 g B in the ideal model. Evaporating the filtrate yields 25 g A, with 200 g water moving to the surroundings. A recovery becomes 100%, but twice as much solvent must be removed. The model does not calculate the needed energy, time or environmental impact; those are additional design criteria.

Transfer: for 50 g A, 10 g B and 200 g water, predict the filter residue, recovered A, recovery percentage and final total including surroundings. Then propose a change that would eliminate A from the filter residue within the available control range.

Check the separation ledger

Capacity is 40 g A. Residue contains 10 g A and 10 g B, recovered A is 40 g, and A recovery is 80%. Final total is 20 + 40 + 200 = 260 g. At 250 g water, capacity is 50 g A, so all A can pass into the filtrate under the assumptions.

Write a testable virtual procedure

Specify component identities and amounts, the basis of the solubility ratio, mixing/equilibration assumptions, which fraction is retained at each step, and how each fraction would be checked. Predict a failure: incomplete dissolution leaves A in the residue; a wet product overstates dry recovered mass; particles passing the filter can contaminate the filtrate.

This model omits retained liquid in the filter cake, adsorption, transfer loss, decomposition and imperfect filtration. Its complete evaporation step is an accounting assumption, not an unsupervised heating instruction. Save a failed separation and an improved comparison, then justify a further measurement that could falsify your purity or recovery claim.