lab questions
1. does a substance have to be water soluble to be classified as hydrophilic? ______ (1 point)
2. group all substances from two lists below into polar, nonpolar and ionic.
from table 1: table sugar, starch, vegetable oil, cellulose, polypropylene, polystyrene;
more compounds: ch₃oh, c₈h₁₈, nacl, c₁₄h₁₀, h₂o, c₂h₅oh, caco₃, nahco₃, c₁₀h₈.
ionic: ____________, ____________, ____________ (1 pt)
polar molecular (covalent): ______, ______, ______, ______, ______, ______ (1 pt)
nonpolar molecular (covalent): ______, ______, ______, ______, ______, ______ (1 pt)
3. do you expect the following ionic compounds to be soluble or insoluble in water?
explain your answer (use ionic compounds solubility rules, do not use word “polar” here).
sodium sulfate ______________________________ (0.5 point)
iron(iii) sulfate ______________________________ (0.5 point)
calcium chloride ______________________________ (0.5 point)
calcium phosphate ______________________________ (0.5 point)
4. do you expect the following substances be soluble or insoluble in (miscible or immiscible with)
water? explain your answer using the “like dissolves like” rule (use the rule, not just write “like
dissolves like”).
ethanol c₂h₅oh ______________________________ (0.5 point)
naphthalene c₁₀h₈ ______________________________ (0.5 point)
isopropanol c₃h₈oh ______________________________ (0.5 point)
isooctane c₈h₁₈ ______________________________ (0.5 point)

Question

Accepted Answer

### Question 1
# Brief Explanations:
Hydrophilic substances have an affinity for water. While high water solubility is common, a substance can be hydrophilic if it interacts favorably with water (e.g., via hydrogen bonding, ion - dipole interactions) even if not fully soluble (like some colloidal or partially soluble substances). So the answer is no.
# Answer:
No

### Question 2
#### Ionic
# Brief Explanations:
Ionic compounds are made of ions. $NaCl$ (sodium chloride), $CaCO_3$ (calcium carbonate), $NaHCO_3$ (sodium bicarbonate) are ionic as they consist of positive and negative ions.
# Answer:
$NaCl$, $CaCO_3$, $NaHCO_3$

#### Polar molecular (covalent)
# Brief Explanations:
Polar covalent molecules have a dipole moment. $CH_3OH$ (methanol), $H_2O$ (water), $C_2H_5OH$ (ethanol) have polar - OH groups and a polar bond distribution. Table sugar (sucrose) and starch, cellulose (polysaccharides with polar - OH groups) are also polar molecular (covalent in parts, with polar functional groups).
# Answer:
table sugar, $CH_3OH$, $H_2O$, $C_2H_5OH$, starch, cellulose

#### Nonpolar molecular (covalent)
# Brief Explanations:
Nonpolar covalent molecules have a symmetric electron distribution. Vegetable oil (triglycerides with long nonpolar hydrocarbon chains), polypropylene, polystyrene (polymers with nonpolar hydrocarbon backbones), $C_8H_{18}$ (isooctane, hydrocarbon), $C_{14}H_{10}$ (naphthalene - like, nonpolar), $C_{10}H_8$ (naphthalene) are nonpolar.
# Answer:
vegetable oil, polypropylene, polystyrene, $C_8H_{18}$, $C_{14}H_{10}$, $C_{10}H_8$

### Question 3
#### Sodium sulfate
# Brief Explanations:
Ionic solubility rule: Sulfates are soluble except for $Ba^{2+}$, $Pb^{2+}$, $Ca^{2+}$ (slightly). Sodium is a group 1 metal. Group 1 metal sulfates are soluble. So sodium sulfate is soluble.
# Answer:
Soluble (because sulfates of group 1 metals are soluble according to ionic solubility rules)

#### Iron(III) sulfate
# Brief Explanations:
Ionic solubility rule: Sulfates are soluble except for $Ba^{2+}$, $Pb^{2+}$, $Ca^{2+}$ (slightly). Iron(III) is not in the exception list. So iron(III) sulfate is soluble.
# Answer:
Soluble (because sulfates of $Fe^{3+}$ are soluble as $Fe^{3+}$ is not in the sulfate - insoluble ion list)

#### Calcium chloride
# Brief Explanations:
Ionic solubility rule: Chlorides are soluble except for $Ag^+$, $Pb^{2+}$, $Hg_2^{2+}$. Calcium is not in the exception list. So calcium chloride is soluble.
# Answer:
Soluble (because chlorides of $Ca^{2+}$ are soluble as $Ca^{2+}$ is not in the chloride - insoluble ion list)

#### Calcium phosphate
# Brief Explanations:
Ionic solubility rule: Phosphates are insoluble except for group 1 metals and ammonium. Calcium is not a group 1 metal or ammonium. So calcium phosphate is insoluble.
# Answer:
Insoluble (because phosphates are insoluble except for group 1 metals and $NH_4^+$, and $Ca^{2+}$ is not in that category)

### Question 4
#### Ethanol $C_2H_5OH$
# Brief Explanations:
"Like dissolves like" rule: Water is polar. Ethanol has a polar - OH group and a nonpolar hydrocarbon chain, but the - OH group can form hydrogen bonds with water. So it is miscible (soluble) in water as it has a polar part that interacts with polar water.
# Answer:
Soluble (miscible). Ethanol is polar (due to - OH group) and can form H - bonds with water (polar), so "like dissolves like" (polar ethanol dissolves in polar water).

#### Naphthalene $C_{10}H_8$
# Brief Explanations:
"Like dissolves like" rule: Water is polar. Naphthalene is a nonpolar hydrocarbon. Nonpolar substances do not interact well with polar water. So it is insoluble (immiscible) in water.
# Answer:
Insoluble (immiscible). Naphthalene is nonpolar and water is polar. According to "like dissolves like", nonpolar does not dissolve in polar, so it is insoluble in water.

#### Isopropanol $C_3H_8OH$
# Brief Explanations:
"Like dissolves like" rule: Water is polar. Isopropanol has a polar - OH group that can form hydrogen bonds with water. So it is miscible (soluble) in water as it has a polar part to interact with polar water.
# Answer:
Soluble (miscible). Isopropanol is polar (due to - OH group) and can form H - bonds with water (polar), so "like dissolves like" (polar isopropanol dissolves in polar water).

#### Isooctane $C_8H_{18}$
# Brief Explanations:
"Like dissolves like" rule: Water is polar. Isooctane is a nonpolar hydrocarbon. Nonpolar substances do not interact well with polar water. So it is insoluble (immiscible) in water.
# Answer:
Insoluble (immiscible). Isooctane is nonpolar and water is polar. According to "like dissolves like", nonpolar does not dissolve in polar, so it is insoluble in water.

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Ionic