Placement test AS Level Chemistry V01

1) What is the maximum volume of butane that can be completely burned in 39 cm³ of oxygen at room temperature and pressure?

C₄H₁₀(g) + 6.5O₂(g) → 4CO₂(g) + 5H₂O(l)

2) What is the expected bond angle in an oxygen difluoride molecule, OF₂?

3) Which is the simplest ionic equation for an alkali reacting with an acid? 

4) Using the isotopic abundance data provided, calculate the relative atomic mass of a sample of silicon. Additionally, in the mass spectrum of silicon, there is a small peak at m/z = 14. Deduce the formula of this particle.

 

Isotope	Abundance (%)
28Si	91.07
29Si	4.62
30Si	3.00
31Si	1.31

5) Calculate the maximum volume, in cm³, of carbon dioxide gas released by the neutralisation reaction with methanoic acid, HCOOH, from 5.00g of baking powder, in an oven at 190°C at 101,000 Pa. Baking powder contains 30% sodium hydrogencarbonate by mass. [pV = nRT, R = 8.31 J/mol K, A_r of H = 1, C = 12, O = 16, and Na = 23]

6) The acidic derivative of tartaric acid contains 20.8% potassium, 25.5% carbon, 2.66% hydrogen by mass and the rest is oxygen. Which of the following is the empirical formula of this compound?

7) Pure silver cups are too soft so small amounts of copper are added to make an alloy. What is the major reason why copper makes the silver less malleable?

1) An enthalpy level diagram for a reaction with an intermediate is shown.

 

2) Which compound has the highest boiling temperature?

3) Group 2 compounds give different colours in a flame test. Which of the following is the best explanation that the cations of Group 2 have different colours in a flame test?

4) When halogenoalkanes are heated with potassium hydroxide, the products depend on the conditions. State what condition, other than a suitable temperature and concentration of potassium hydroxide, would give a high yield of but‑1‑ene and but‑2‑ene from 2‑chlorobutane.

5) Which of the following is the IUPAC name of the product formed by complete hydrogenation of myrcene with hydrogen presence in platinum.

 

6) Bromine and chlorine each have two stable isotopes, ⁷⁹Br, ⁸¹Br, ³⁵Cl and ³⁷Cl. Which statement is true?

7) In a titration between a CH₃COOH (weak acid) and a NH₃ (weak base) indicators do not give a distinct colour change. The reaction that occurs is shown.

CH₃COOH(aq) + NH₃(aq) → CH₃COONH₄(aq)

So other techniques must be used. One technique is thermometric titration.

Procedure 

Step 1 The temperature of 30.0 cm³ of dilute ethanoic acid in a polystyrene cup is recorded. 

Step 2 Ammonia solution of concentration 1.30 mol dm^-3 is added to the acid in the polystyrene cup in separate 5.00 cm³ portions. After each addition the mixture is stirred and the temperature measured.

A student carried out the experiment and plotted the graph and the initial and final temperature is 20.9 and 27.6 ^oC, respectively. Which of the following is the enthalpy change of neutralisation for this reaction, in kJ mol^-1. [Assume that the density of all solutions is 1.00 g cm^-3 and that the specific heat capacity of all solutions is 4.18 J g^-1 °C^-1]