40 report sheet • separation of the components of a mixture
7. how does this experiment illustrate the principle of conservation of matter?
8. a mixture was found to contain 1.05 g of sio₂, 0.69 g of cellulose, and 1.82 g of calcium carbonate. what percentage of calcium carbonate is in the mixture?
9. how could you separate a mixture of acetone and α-naphthol? consult table 2.1 for physical properties.
10. how could you separate zinc chloride from sio₂?
11. a student found that her mixture was 13% nh₄cl, 18% nacl, and 75% sio₂. assuming that her calculation are correct, what did she most likely do incorrectly in her experiment?
12. why is the nacl extracted with water three times as opposed to only once?

Question

Accepted Answer

### Question 8
# Explanation:
## Step1: Calculate total mass of mixture
First, find the total mass of the mixture by adding the masses of all components. The masses are $1.05\ \text{g}$ (SiO₂), $0.69\ \text{g}$ (cellulose), and $1.82\ \text{g}$ (calcium carbonate). So total mass $m_{\text{total}} = 1.05 + 0.69 + 1.82$.
$m_{\text{total}} = 1.05 + 0.69 + 1.82 = 3.56\ \text{g}$

## Step2: Calculate percentage of calcium carbonate
The formula for percentage composition is $\text{Percentage} = \frac{\text{Mass of component}}{\text{Total mass of mixture}} \times 100\%$. For calcium carbonate, mass is $1.82\ \text{g}$ and total mass is $3.56\ \text{g}$. So percentage $= \frac{1.82}{3.56} \times 100\%$.
$\frac{1.82}{3.56} \times 100\% \approx 51.12\%$ (rounded to two decimal places)

# Answer:
The percentage of calcium carbonate in the mixture is approximately $51.12\%$ (or more precisely, $\frac{1.82}{1.05 + 0.69 + 1.82} \times 100\% \approx 51.1\%$ depending on rounding during steps).

### Question 10
# Brief Explanations:
Zinc chloride ($ZnCl_2$) is soluble in water, while silicon dioxide ($SiO_2$) is insoluble in water. To separate them, we can use the following steps:
1. Add the mixture to a beaker of water and stir thoroughly. This will dissolve the $ZnCl_2$ in the water, leaving the $SiO_2$ as a solid residue.
2. Filter the mixture using filter paper and a funnel. The solid $SiO_2$ will be trapped on the filter paper, and the filtrate (aqueous solution of $ZnCl_2$) will pass through.
3. To recover $ZnCl_2$ from the filtrate, we can evaporate the water (e.g., using a hot plate or evaporating dish) to obtain solid $ZnCl_2$.

# Answer:
To separate zinc chloride ($ZnCl_2$) from $SiO_2$: dissolve the mixture in water (since $ZnCl_2$ is soluble and $SiO_2$ is insoluble), filter to remove solid $SiO_2$, then evaporate the filtrate to recover $ZnCl_2$.

### Question 7
# Brief Explanations:
The principle of conservation of matter (mass) states that matter is neither created nor destroyed in a chemical or physical process, so the total mass of substances before and after a process should be equal (or account for any losses due to experimental error like evaporation, but in ideal cases, conserved). In a mixture separation experiment (e.g., separating components like $NH_4Cl$ (sublimes), $NaCl$ (soluble), $SiO_2$ (insoluble)):
- Initially, we have a mixture with a total mass (sum of all components).
- After separation (e.g., subliming $NH_4Cl$, dissolving/filtering $NaCl$ and $SiO_2$, then recovering each component), the sum of the masses of the separated components should approximately equal the initial total mass (considering minor losses like some $NH_4Cl$ not fully sublimed, or $NaCl$ left in filter paper, etc.). For example, if you start with a mixture of $NH_4Cl$, $NaCl$, and $SiO_2$, after subliming $NH_4Cl$ (collecting the sublimate), dissolving the remaining solid in water, filtering to get $SiO_2$ (drying it), and evaporating the filtrate to get $NaCl$, the sum of the mass of $NH_4Cl$ sublimate, dried $SiO_2$, and recovered $NaCl$ should be close to the initial mixture mass. This shows that the total mass (matter) is conserved through the physical processes (sublimation, dissolution, filtration, evaporation) used to separate the mixture—matter was just separated into its components, not created or destroyed.

# Answer:
In the mixture separation experiment, the total mass of the separated components (after processes like sublimation, dissolution, filtration, evaporation) should approximately equal the initial mixture’s mass (accounting for minor losses), illustrating that matter (mass) is conserved (neither created nor destroyed) during the physical separation processes.

### Question 9
# Brief Explanations:
To separate acetone and $\alpha$-naphthol, we use their different physical properties (from Table 2.1, likely boiling points or solubility, but acetone is a volatile liquid (low boiling point, ~56°C) and $\alpha$-naphthol is a solid with higher boiling point/solubility differences). Distillation is suitable:
1. Set up a distillation apparatus (flask with mixture, condenser, receiver).
2. Heat the mixture. Acetone, being more volatile (lower boiling point), will vaporize first.
3. The acetone vapor travels to the condenser, where it cools and condenses back to liquid, collected in the receiver.
4. $\alpha$-naphthol, with higher boiling point, remains as a solid (or liquid residue if heated enough but less volatile) in the distillation flask.

(Alternative: If solubility differs, e.g., acetone is miscible with water, $\alpha$-naphthol has limited solubility, but distillation is more direct for volatile liquid + less volatile solid/liquid.)

# Answer:
Separate acetone and $\alpha$-naphthol by **distillation**: heat the mixture, vaporize the more volatile acetone, condense it (in a condenser), and collect the condensed acetone; $\alpha$-naphthol remains in the distillation flask.

### Question 11
# Brief Explanations:
The student’s calculated percentages ($13\% + 18\% + 75\% = 106\%$) exceed $100\%$, which is impossible for percentage composition (sum must be $100\%$ for a mixture’s components). Likely errors:
- **Incomplete separation/loss of mass not accounted for**: E.g., when separating $NH_4Cl$ (sublimes), $NaCl$ (soluble), $SiO_2$ (insoluble), she may have:
  - Not fully sublimed $NH_4Cl$ (so some $NH_4Cl$ remained with $NaCl/SiO_2$, leading to overcounting $NH_4Cl$ or other components).
  - Not fully dried $SiO_2$ (so its mass included water, inflating $SiO_2$’s percentage).
  - Not fully recovered $NaCl$ (but here the sum is over, so more likely an overestimation: e.g., $NH_4Cl$ not fully removed (so counted in both $NH_4Cl$ and another component), or $SiO_2$ was wet (extra mass), or $NaCl$ had impurities. The key is the sum of percentages is >100%, so she likely **overestimated the mass of one or more components** (e.g., incomplete drying of a component, or not fully separating a component, leading to double-counting or extra mass in a component’s measurement).

# Answer:
The sum of her percentages ($13\% + 18\% + 75\% = 106\%$) exceeds $100\%$, so she most likely **overestimated the mass of one or more components** (e.g., incomplete drying of $SiO_2$ (water added to its mass), not fully separating $NH_4Cl$ (so it was counted in another component’s mass), or similar errors leading to overcounting mass for components).

### Question 12
# Brief Explanations:
Extracting $NaCl$ with water three times (instead of once) is based on the principle of **multiple extractions** to maximize the amount of $NaCl$ dissolved (and thus separated from insoluble components like $SiO_2$).
- When extracting (dissolving $NaCl$ from a mixture with $SiO_2$), a single extraction with a large volume of water or multiple extractions with smaller volumes (total volume same) follows the distribution of solute between phases.
- Multiple extractions (smaller, repeated water additions) are more efficient: each time, we dissolve more of the remaining $NaCl$ from the solid mixture. After the first extraction, some $NaCl$ remains undissolved; a second extraction dissolves more of the remaining, and a third dissolves even more (approaching maximum recovery).
- If done once, a significant amount of $NaCl$ might remain adsorbed on the insoluble $SiO_2$ or not fully dissolved, leading to lower recovery. So three extractions increase the yield (amount) of $NaCl$ extracted from the mixture.

# Answer:
Extracting $NaCl$ with water three times (vs. once) is more efficient for maximizing $NaCl$ recovery: each repeated extraction dissolves more remaining $NaCl$ from the mixture (due to the distribution of solute between phases), reducing the amount of $NaCl$ left with the insoluble component ($SiO_2$) and increasing the total $NaCl$ extracted.

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Explanation:

Question 8

Step1: Calculate total mass of mixture

Step2: Calculate percentage of calcium carbonate

Answer:

Question 10