Practice Paper 2 (SL IB Chemistry)

Nitroglycerin is an oily, colourless liquid and a high explosive, discovered by Alfred Nobel. The unbalanced equation for its explosive decomposition is given below. 

........C₃H₅N₃O₉ (l)  → .......N₂ (g) +   ......CO (g) + .......H₂O (g) + .......O₂ (g)

Deduce the coefficients required to balance the equation for this reaction and use the equation to suggest why nitroglycerin acts as a high explosive.

Nitroglycerin is also used medicinally to treat angina attacks. It comes in the form of tablets, ointments, skin patches and nasal sprays. Nasal sprays vaporise the nitroglycerin, so it is quickly absorbed in the body.

A commercial 11.2 g nasal spray pump delivers a metered dose of exactly 400 micrograms of nitroglycerin. Determine the number of moles present in one dose and how many doses a spray pump can deliver.

Suggest a reason why the actual number of doses delivered by the spray pump is less than you have calculated in (b).

Electron configurations give you a summary of where you can find an electron around the nucleus of an atom. They can also be determined for an ion after an atom loses or gains electrons.

State the full electron configuration of the rubidium ion, . 

The element rubidium has two naturally occurring isotopes of ⁸⁵Rb and ⁸⁷Rb. The relative atomic mass of rubidium is 85.47. Calculate the percentage abundance of each isotope.

The electrons in an atom are found in orbitals around the nucleus, which have different energy levels sometimes called shells.

Rubidium forms an ionic compound with selenium, Rb₂Se. Using boxes to represent orbitals and arrows to represent electrons, sketch the orbital diagram of the valence shell of selenium on the axis provided.

Figure 1

Gas cylinders of helium, like the one shown below, are sometimes used to inflate party balloons.

Figure 1

A typical 11-inch party balloon has a fully inflated volume of 14.1 dm³. The pressure in the gas cylinders is 20,000 kPa. If the gas cylinder can fill 160 balloons at 298 K and 108 kPa, what is the total volume of helium inside the gas cylinder in dm³?

Sketch a graph to show the relationship between the volume and temperature of an ideal gas at constant pressure. Describe the relationship between the two variables.

Deep sea divers sometimes breathe mixtures of helium and oxygen in their scuba diving tanks when the conditions are very deep, so they can avoid nitrogen narcosis.

If a bubble of gas escapes from a scuba tank at 60 m depth where the pressure is 588 kPa and the temperature is 8 ^oC, determine the increase in the size of the bubble by the time it reaches the surface where the pressure is 100 kPa and the temperature is 20 ^oC.

Commercial aircraft are fitted with oxygen cannisters that provide a supply of oxygen in case of the loss of cabin pressure. The cannisters contain sodium chlorate(V) which produces oxygen in the following decomposition reaction.

2NaClO₃ (s) " 2NaCl (s) + 3O₂ (g)

Determine the mass of sodium chlorate(V) needed to produce 10.0 dm³ of oxygen at 298 K and 90 kPa.

Suggest why elements are found at the bottom of a triangular bonding diagram.

Suggest the position of ionic and covalent materials within a triangular bonding diagram. Explain your answer. 

Name the x-axis and y-axis on a standard triangular bonding diagram.

x-axis: ..................................................

y-axis: ..................................................

Using Sections 9 and 17 of the Data Booklet, plot nitrogen trifluoride (NF₃) on the triangular bonding diagram.

A molecule of oleic acid is shown.

Oleic acid is a fatty acid which occurs naturally in different animals and plants.

Oleic acid exhibits stereoisomerism. Explain the meaning of this term and identify why oleic acid has stereoisomers.

Crotonic acid is another fatty acid which has a similar structure to oleic acid. The molecular formula of crotonic acid is C₄H₆O₂. 

For the reaction profile outlined in the reaction profile below, state the mechanism or type of reaction for steps 1 and 2. 

Propane  1-bromopropane  Compound X  Propanal 

Step 1 ...............................................................

Step 2 ...............................................................

Compound X can be oxidised by the reaction with acidified potassium dichromate to give propanal. Compound X will oxidise to propanoic acid if allowed to fully oxidise. Explain how full oxidation can be prevented.