DP Chemistry Questionbank

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.

The amount of proteins, fats and carbohydrates determine the energy content of foods.

Explain why linoleic acid, C₁₈H₃₂O₂, is a more efficient energy storage molecule than raffinose, C₁₈H₃₂O₁₆.

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.

Solid fat triglycerides can also clog kitchen sink drains.

Explain how sodium hydroxide unblocks the drain.

List the building blocks of triglycerides and carbohydrates.

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

10.0 g of sunflower oil reacts completely with 123 cm³ of 0.500 mol$$dm^–3 iodine solution. Calculate the iodine number of sunflower oil to the nearest whole number.

Glycerol is one product of the reaction. Identify the two other organic products.

Identify the type of reaction which occurs.

Deduce the products of the hydrolysis of a non-substituted phospholipid, where ${\mathrm{R}}^1$ and ${\mathrm{R}}^2$ represent long alkyl chains.

Phospholipids help maintain cellular environments while fatty acid lipids have important roles in energy storage and electrical insulation. Discuss the structural properties of saturated fats needed for these roles.

A representation of a phospholipid bilayer cell membrane is shown:

© International Baccalaureate Organization 2020.

Identify the components of the phospholipid labelled A and B.

Outline the importance of linoleic acid for human health.

Calculate the volume of iodine solution used to reach the end-point. 

State one factor that increases the rate at which saturated lipids become rancid.

Fish oil is an excellent dietary source of omega-3 fatty acids. Outline one impact on health of consuming omega-3 fatty acids.

Butter contains varying proportions of oleic, myristic, palmitic and stearic acids. Explain in terms of their structures why stearic acid has a higher melting point than oleic acid, using section 34 of the data booklet.

Identify the type of rancidity occurring in saturated lipids and the structural feature that causes it.

Deduce the structure of the lipid formed by the reaction between lauric acid and glycerol (propane-1,2,3-triol) using section 34 of the data booklet.

Outline one impact food labelling has had on the consumption of foods containing different types of lipids.

Arachidonic acid is a polyunsaturated omega-6 fatty acid found in peanut oil.

Determine the number of carbon–carbon double bonds present if the iodine number for the compound is 334. (Arachidonic acid M_r = 304.5)

Explain why lipids provide more energy than carbohydrates and proteins.

The iodine number is the maximum mass of iodine that reacts with 100 g of an unsaturated compound.

Determine the iodine number of stearidonic acid, C₁₇H₂₇COOH.

The iodine number is the maximum mass of iodine that reacts with 100 g of an unsaturated compound.

Determine the iodine number of stearidonic acid, C₁₇H₂₇COOH.

Fats contain triglycerides that are esters of glycerol and fatty acids. Deduce an equation for the acid hydrolysis of the following triglyceride.

The melting points of cocoa butter and coconut oil are 34 °C and 25 °C respectively.

Explain this in terms of their saturated fatty acid composition.

The addition of partially hydrogenated cocoa butter to chocolate increases its melting point and the content of trans-fatty acids (trans-fats).

Outline one effect of trans-fatty acids on health.

Deduce the structural formula of phosphatidylcholine.

Lecithin is a major component of cell membranes. Describe the structure of a cell membrane.

Phospholipids are also found in lipoprotein structures.

Describe one effect of increased levels of low-density lipoprotein (LDL) on health.

The melting points of cocoa butter and coconut oil are 34 °C and 25 °C respectively.

Explain this in terms of their saturated fatty acid composition.

The addition of partially hydrogenated cocoa butter to chocolate increases its melting point and the content of trans-fatty acids (trans-fats).

Outline two effects of trans-fatty acids on health.

Fats contain triglycerides that are esters of glycerol and fatty acids. Deduce an equation for the acid hydrolysis of the following triglyceride.

Deduce the structural formula of phosphatidylcholine.

Lecithin is a major component of cell membranes. Describe the structure of a cell membrane.

Phospholipids are also found in lipoprotein structures.

Describe two effects of increased levels of low-density lipoprotein (LDL) on health.

Predict, giving a reason, the relative energy density of a carbohydrate and a lipid of similar molar mass.

The iodine number is the number of grams of iodine which reacts with 100 g of fat. Calculate the iodine number of oleic acid.

Identify a reagent that hydrolyses triglycerides.

The chemical change in stored fats causes rancidity characterized by an unpleasant smell or taste.

Compare hydrolytic and oxidative rancidity.

The iodine number is the number of grams of iodine which reacts with 100 g of fat. Calculate the iodine number of oleic acid.