Practice Paper 2 (SL IB Chemistry)

This question is about line emission spectra of elements.

The visible line emission spectrum of hydrogen is shown below in Figure 1 and the wavelengths of the first four lines are listed in Table 1.

Figure 1

The visible line emission spectrum hydrogen

 Table 1

Draw the shape of a 1s atomic orbital and 2p atomic orbital.    

Describe the relationship between colour, energy, frequency, and wavelength in the visible spectrum.

A group of students planned how to investigate the effect of changing the concentration of H₂SO₄ on the initial rate of reaction with magnesium: 

Mg (s) + H₂SO₄ (aq) MgSO₄ (aq) + H₂ (g) 

They decided to measure how long the reaction took to complete when similar masses of magnesium were added to acid. 

Two methods were suggested:

Method 1 - Use small pieces of magnesium ribbon, an excess of acid and record the time taken for the magnesium ribbon to disappear

Method 2 - Use large strips of magnesium ribbon, an excess of magnesium and record the time taken for bubbles to stop forming 

Deduce, giving a reason, which of method 1 and method 2 would be the least affected if the masses of magnesium ribbon used varied slightly between each experiment.

Neither method in part a) actually allows the initial rate to be calculated. Outline a method that would allow the calculation of initial rate.

The reaction is to be conducted across a few weeks.

State a factor that has a significant effect on reaction rate, which could vary between experiments across the weeks and therefore needs to be controlled.

One group collected the following data using 1.50 mol dm^-3 acid:

Trial	Time/ s ( 0.01 s)
1	91.56
2	98.33
3	72.08
4	89.41

Calcium nitrate contains both covalent and ionic bonds.

State the formula of both ions present and the nature of the force between these ions.

State the formula of the compound that boron forms with chlorine.

Draw the Lewis structure for boron chloride.

Define the term standard enthalpy of combustion, ΔH^ϴ_c.

Write an equation for the complete combustion of propanol, CH₃CH₂CH₂OH (l).

Construct a Hess’s Law cycle for the complete combustion of propanol.

Table 1

Malonic acid is a naturally occurring acid found in fruits and vegetables and is shown in Figure 1.

Figure 1 

The first dissociation of malonic acid is:

C₃H₄O₄ (aq) + H₂O (l) ⇌ C₃H₃O₄^- (aq) + H₃O⁺ (aq)

Identify one conjugate acid-base pair from the equation.

The equilibrium constant for the first dissociation of malonic acid is 1.48 x 10^-3.

State, with a reason, the strength of malonic acid.

The anion C₃H₃O₄^- may be classified as amphiprotic. Explain the meaning of amphiprotic and write equations, using C₃H₃O₄^-_, to illustrate your answer.

The formulae of four organic compounds are given in Table 1. Write the names of the compounds in the second column.

Table 1

Which of the compounds in part (a) are structural isomers of each other and what type of isomerism do they show?