DP Chemistry Questionbank

Explain why the boiling point of ethane-1,2-diol is significantly greater than that of ethene.

The table below shows average figures for the percentage fatty acid composition of some common fats and oils.

(i) Deduce, with a reason, which fat or oil from the table above has the lowest iodine number.

(ii) Deduce, with a reason, which fat or oil from the table above is most likely to become rancid when exposed to the air.

(iii) The P/S index of a fat or oil is the ratio of polyunsaturated fat to saturated fat present. It is sometimes used to compare the relative health benefits of different lipids in the diet. Calculate the P/S index of beef fat and soybean oil.

(iv) Suggest why a P/S index of greater than 1 is considered beneficial to health.

(v) Cotton seed oil and corn oil have similar iodine numbers but the melting point of cotton seed oil is higher than that of corn oil. Suggest an explanation in terms of the structure and bonding in these two oils.

(i) Uranium hexafluoride, UF₆, is used in the uranium enrichment process that produces fuel for nuclear reactors.

State the molecular shape of uranium hexafluoride.

(ii) Explain why uranium dioxide, UO₂, has a very high melting point whereas uranium hexafluoride vapourises easily into gas.

The solubility of a vitamin depends on its structure.

Identify the vitamin given in section 35 of the data booklet that is the most soluble in water.

A chloride of titanium, TiCl₄, melts at 248 K. Suggest why the melting point is so much lower than that of KCl.

The drain pipe of a kitchen sink can become clogged by fatty acids, such as linoleic acid, C₁₈H₃₂O₂, but not by the trisaccharide, raffinose, C₁₈H₃₂O₁₆, containing the same number of carbon atoms.

Explain why raffinose is far more water soluble than linoleic acid.

Explain why the difference in their structures affects their melting points.

Suggest why aspirin is slightly soluble in water. Refer to section 37 of the data booklet.

State why hydrazine has a higher boiling point than dinitrogen tetraoxide.

Which bonds cause the boiling point of water to be significantly greater than that of hydrogen sulfide?

A.     London (dispersion)

B.     Covalent

C.     Ionic

D.     Hydrogen

Explain which one of these fatty acids has the highest boiling point.

Suggest, in terms of its structure, why vitamin D is fat-soluble using section 35 of the data booklet.

Explain why diamorphine passes more readily than morphine through the blood-brain barrier.

Suggest why a non-polar solvent was needed.

Proteins are polymers of amino acids.

The mixture is composed of glycine, $\mathrm{Gly}$, and isoleucine, $\mathrm{Ile}$. Their structures can be found in section 33 of the data booklet.

Deduce, referring to relative affinities and ${\mathrm{R}}_{\mathrm{f}}$, the identity of A1.

State the most significant intermolecular forces in the phospholipid in b(i).

Proteins are polymers of amino acids.

The mixture is composed of glycine, $\mathrm{Gly}$, and isoleucine, $\mathrm{Ile}$. Their structures can be found in section 33 of the data booklet.

Deduce, referring to relative affinities and ${\mathrm{R}}_{\mathrm{f}}$, the identity of A1.

Explain why the melting points of the group 1 metals (Li → Cs) decrease down the group whereas the melting points of the group 17 elements (F → I) increase down the group.

Explain how the inclusion of carbohydrates in plastics makes them biodegradable.

Identify the type of intermolecular bonding that is responsible for Kevlar^®’s strength.

Explain why the melting points of the group 1 metals (Li → Cs) decrease down the group.

Explain, at the molecular level, why vitamin D is soluble in fats. Use section 35 of the data booklet.

Describe how the structures of LDPE and HDPE affect one mechanical property of the plastics.

Suggest one reason why urea is a solid and ammonia a gas at room temperature.

Sketch two different hydrogen bonding interactions between ammonia and water.

Carbon and silicon are elements in group 14.

Explain why CO₂ is a gas but SiO₂ is a solid at room temperature.

What are the strongest intermolecular forces between molecules of propanone, CH₃COCH₃, in the liquid phase?

A.     London (dispersion) forces

B.     Covalent bonding

C.     Hydrogen bonding

D.     Dipole–dipole forces

Suggest one reason why urea is a solid and ammonia a gas at room temperature.

Sketch two different hydrogen bonding interactions between ammonia and water.

Part of this molecule is hydrophilic (bonds readily to water) and part hydrophobic (does not bond readily to water). Draw a circle around all of the hydrophilic part of the molecule.

When a small amount of palmitic acid is placed in water it disperses to form a layer on the surface that is only one molecule thick. Explain, in terms of intermolecular forces, why this occurs.

The compounds shown below have similar relative molecular masses. What is the correct order of increasing boiling point?

A.     CH₃COOH < (CH₃)₂CO < (CH₃)₂CHOH

B.     CH₃COOH < (CH₃)₂CHOH < (CH₃)₂CO

C.     (CH₃)₂CO < CH₃COOH < (CH₃)₂CHOH

D.     (CH₃)₂CO < (CH₃)₂CHOH < CH₃COOH

Suggest a reason that the Winkler Method used to measure biochemical oxygen demand (BOD) must be done at constant temperature.

Suggest why aspirin is slightly soluble in water. Refer to section 37 of the data booklet.

Which statement best describes the intramolecular bonding in HCN (l)?

A. Electrostatic attractions between H⁺ and CN⁻ ions

B. Hydrogen bonding

C. Van der Waals forces and hydrogen bonding

D. Electrostatic attractions between pairs of electrons and positively charged nuclei

What is the main interaction between liquid CH₄ molecules?

A.  London (dispersion) forces

B.  Dipole–dipole forces

C.  Hydrogen bonding

D.  Covalent bonding

Suggest why hydrogen chloride, HCl, has a lower boiling point than hydrogen cyanide, HCN.

Explain why C₆₀ and diamond sublime at different temperatures and pressures.

Suggest how benzoic acid, M_r = 122.13, forms an apparent dimer, M_r = 244.26, when dissolved in a non-polar solvent such as hexane.

Identify the type of interaction that must be overcome when liquid ethyne vaporizes.

Explain why product B is water soluble.

What is the order of increasing boiling point?

A. CH₃CH₂CH₂CH₃ < CH₃CH(OH)CH₃ < CH₃COCH₃ < CH₃CO₂H

B. CH₃CH₂CH₂CH₃ < CH₃COCH₃ < CH₃CH(OH)CH₃ < CH₃CO₂H

C. CH₃CO₂H < CH₃COCH₃ < CH₃CH(OH)CH₃ < CH₃CH₂CH₂CH₃

D. CH₃CH₂CH₂CH₃ < CH₃COCH₃ < CH₃CO₂H < CH₃CH(OH)CH₃

Suggest how benzoic acid, M_r = 122.13, forms an apparent dimer, M_r = 244.26, when dissolved in a non-polar solvent such as hexane.

Identify the type of interaction that must be overcome when liquid ethyne vaporizes.

Explain why product B is water soluble.

What is the order of increasing boiling point?

A. CH₃CH₂CH₂CH₃ < CH₃CH(OH)CH₃ < CH₃COCH₃ < CH₃CO₂H

B. CH₃CH₂CH₂CH₃ < CH₃COCH₃ < CH₃CH(OH)CH₃ < CH₃CO₂H

C. CH₃CO₂H < CH₃COCH₃ < CH₃CH(OH)CH₃ < CH₃CH₂CH₂CH₃

D. CH₃CH₂CH₂CH₃ < CH₃COCH₃ < CH₃CO₂H < CH₃CH(OH)CH₃

Explain why the compound C₃H₈O, produced in (a)(iv), has a higher boiling point than compound C₃H₆O, produced in d(i).

Explain why the compound C₂H₆O, produced in (b), has a higher boiling point than compound C₂H₄O, produced in d(i).