1. a) Concrete: Heterogeneous mixture b) Tomato juice: Homogeneous mixture c) Marble: Pure substance d) Seawater: Homogeneous mixture e) Iron: Pure substance

Decantation is a method of separating a liquid from a solid that has settled to the bottom of the container. Filtration is a method of separating a liquid from a solid by passing it through a porous material that traps the solid. Decantation is generally faster than filtration because it does not require the liquid to be passed through a porous material.

No, you could not determine the amounts of NaCl, NH4Cl, and SiO2 (sand) originally present. The water would dissolve the NaCl and NH4Cl, but it would not dissolve the SiO2 (sand). When the extract and insoluble residue were heated to dryness, the NaCl and NH4Cl would evaporate, leaving behind the SiO2 (sand). However, you would not be able to determine the amounts of NaCl and NH4Cl that were originally present because they would have been evaporated.

The percentage of CaCO3 in the mixture is calculated as follows:

Percentage of CaCO3 = (mass of CaCO3 / total mass of mixture) * 100%

= (6.72 g / (3.10 g + 0.38 g + 6.72 g)) * 100%

= 68.6%

The total percent recovery of the mixture is calculated as follows:

Total percent recovery = (total mass of recovered components / total mass of original mixture) * 100% = (1.32 g + 1.24 g + 0.62 g) / 3.27 g) * 100% = 101%

The total percent recovery is greater than 100% because there is a small error in the experimental measurements.

7. a) No, you could not separate the components of a mixture of Mg(OH)2 and Zn(OH)2 by only using 3 M HCl. Both Mg(OH)2 and Zn(OH)2 are insoluble in 3 M HCl. b) Yes, a mixture of benzoic acid and Mg(OH)2 could be separated by using 3 M NaOH. Benzoic acid is soluble in 3 M NaOH, while Mg(OH)2 is not. To separate the mixture, you would first add 3 M NaOH to the mixture. The benzoic acid would dissolve in the 3 M NaOH, while the Mg(OH)2 would remain undissolved. You could then filter the mixture to remove the Mg(OH)2. To recover the benzoic acid, you would acidify the filtrate with HCl. This would precipitate the benzoic acid, which you could then collect by filtration. c) To separate the components of a mixture of benzoic acid, Mg(OH)2, and Zn(OH)2 and recover both substances, you could follow these steps:
8. Add 3 M NaOH to the mixture until the benzoic acid dissolves.
9. Filter the mixture to remove the Mg(OH)2 and Zn(OH)2.
10. To recover the benzoic acid, acidify the filtrate with HCl. The benzoic acid will precipitate.
11. Filter the mixture to collect the benzoic acid.
12. To recover the Mg(OH)2 and Zn(OH)2, dissolve the precipitate in HCl.
13. Add NaOH to the solution until the Mg(OH)2 and Zn(OH)2 precipitate.
14. Filter the mixture to collect the Mg(OH)2 and Zn(OH)2.

Please note that this is just a general procedure. You may need to modify the steps depending on the specific mixture you are working with.