Chemistry Unit 2 exam Questions PDF

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Unit 2 chemistry exam written by an experienced VCE chemistry teacher (teaches Units 1-4 Chemistry)...

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Unit Two Chemistry 2017

Unit Two Chemistry Exam Multiple Choice

20 marks

You need to record your answers in the appropriate section in the ANSWER BOOKLET. Question 1 When ethanol dissolves in water the bonds formed between the ethanol and water molecules are known as A. B. C. D.

dispersion forces ion-dipole attraction hydrogen bonds ionisation

Question 2 When NaOH dissociates in water, the equation that describes the process is A. B. C. D.

NaOH (s) → Na+ (aq) + OH- (aq) NaOH (s) + H2O (l) → NaO- (aq) + H3O+ (aq) NaOH (s) + H2O (l) → NaOH2+ (aq) + OH- (aq) NaOH (aq) + HCl (aq) → NaCl (s) + H2O (l)

Question 3 How much heat energy is required to raise the temperature of 250 mL of water from 17 0C to 100 0C? Assume that 1 mL of water has a mass of 1 g and that the specific heat capacity of water is 4.2 J g -1 0C-1. A. B. C. D.

8.7 J 87,150 KJ 8.7 KJ 8.7 x 104 J

Question 4 A solution containing 0.25 g of NaCl dissolved in 50 mL of deionised water will have a concentration of A. B. C. D.

5.0 gL-1 4.3 M 5.0 x 10-3 mgL-1 2.5 x 10-4 mol/L

Question 5 A solution of CuSO4 has a concentration of 2.50 M. This concentration is equivalent to A. B. C. D.

399 %m/v 39.9 %m/v 0.250 %m/v 25.0 m/v

Unit Two Chemistry 2017

Question 6 A 10 mL solution of 10 %w/v alcohol solution is diluted with 90 mL of water. The concentration of the resultant solution is A. B. C. D.

1 %w/v 1.11 %w/v 10 %w/v 10 M

Questions 7, 8 and 9 refer to the following information. The sulfate (SO42-) content of a plant fertiliser is to be determined by gravimetrically analysing a 2.5 g sample of fertiliser. Question 7 The first part of this analysis would involve A. B. C. D.

producing a precipitate. filtering the sulfate ions from the insoluble material in the fertiliser. dissolving the sulfate from the fertilser into water. adding an indicator to an aliquot of the sulfate solution.

Question 8 An important part of gravimetric analysis is to react the chemical under analysis with an excess solution in order to produce a precipitate. This solution is known as a precipitating reagent. Which precipitating reagent would be the most suitable for this analysis? A. B. C. D.

NaCl (aq) Ba(NO3)2 (aq) KCl (aq) CuSO4 (aq)

Question 9 Which of the following errors in experimental procedure would produce a % of sulfate in the fertiliser that would be LESS than the true value? A. B. C. D.

Failure to wash the precipitate with distilled water. Failure to dry the precipitate to a constant mass. Failure to add an excess amount of precipitating reagent. Failure to let the precipitate dry in an oven.

Question 10 The ionic equation for the precipitation reaction between silver nitrate and sodium chloride is given by A. B. C. D.

Na+ (aq) + NO3- (aq) → NaNO3 (s) Ag+ (aq) + Cl- (aq) → AgCl (s) AgNO3 (aq) + NaCl (aq) → AgCl (s) + NaNO3 (aq) Ag+ (aq) + NO3- (aq) → AgNO3 (s)

Unit Two Chemistry 2017

Question 11 Which combination of reactants will not produce a gas? A. B. C. D.

NaOH and HCl Zn and HNO3 NaHCO3 and H2SO4 CaCO3 and HCl

Question 12 10.0 mol of Mg reacts with excess HCl solution at 25 0C. The moles of HCl that will react is equal to A. B. C. D.

10.0 mol 5.0 mol 20.0 mol Unable to be determined as the HCl is in excess.

Questions 13, 14 and 15 refer to the following information. A 20 mL aliquot of vinegar is titrated with 15 mL of 0.10 M NaOH. Some of the equipment used for this titration is shown below.

A

B

Question 13 The piece of equipment labelled A on the diagram should be A. B. C. D.

rinsed with distilled water and filled with 20 mL of vinegar. rinsed with distilled water and filled with 0.10 M NaOH. rinsed with 0.10 M NaOH and filled with 0.10 M NaOH. rinsed with vinegar and filled with 20 mL of vinegar.

Question 14 If the equipment labelled A is rinsed with distilled water prior (before) to the titration, A. B. C. D.

the volume of NaOH used will be 15 mL. the volume of vinegar used will be less than 15 mL the volume of NaOH used will be greater than 15 mL. the volume of NaOH used will be exactly 20 mL.

Unit Two Chemistry 2017

Question 15 If the equipment labelled B is rinsed with distilled water prior to the titration, A. B. C. D.

the volume of NaOH used will be 15 mL. the volume of vinegar used will be less than 15 mL the volume of NaOH used will be greater than 15 mL. the volume of NaOH used will be exactly 20 mL.

Question 16 A blue solution of CuSO4 is to be analysed by uv-visible spectroscopy. Part of this analysis will involve A. B. C. D.

passing red light through the solution. passing blue light through a flame containing this solution. passing red light through a flame containing this solution. passing blue light through the solution.

Questions 17 and 18 refer to the following chromatogram.

B A

Question 17 It can be said that A. B. C. D.

A has higher solubility in the solvent than B. B has a greater affinity (attraction) for the stationary phase than A. B formed stronger bonds with the mobile phase than A. B had a greater ability to adsorb onto the stationary phase than A.

Question 18 If the sample containing components A and B was passed through a HPLC column that used the same solvent as that used for the above chromatogram, the retention time of component A would be A. B. C. D.

greater than the retention time for B. less than the retention time for B. equal to the retention time for B. unable to be determined.

Unit Two Chemistry 2017 Question 19 When comparing HPLC with paper chromatography it is correct to say that A. B. C. D.

both can be used to determine that amount of a component present. only HPLC can be used to identify the components present. only paper chromatography uses standards to identify components. both paper chromatography and HPLC use a solid stationary phase.

Question 20 A sample of water is contaminated with a very small amount of lead metal. The most accurate way to determine the amount of lead in the water is to use A. B. C. D.

uv-visible spectroscopy paper chromatography atomic absorption spectroscopy high performance liquid chromatography

End of section A

Unit Two Chemistry 2017

Section A & B Answer Booklet Student’s Name ______________________________

Section A – Multiple Choice Record all your answers to SECTION A – MULTIPLE CHOICE in the table below. You should do this by placing either a cross or circle around the letter corresponding to the answer, which you believe, is the most correct. For example: 21.

A

B

C

D

1.

A

B

C

D

11.

A

B

C

D

2.

A

B

C

D

12.

A

B

C

D

3.

A

B

C

D

13.

A

B

C

D

4.

A

B

C

D

14.

A

B

C

D

5.

A

B

C

D

15.

A

B

C

D

6.

A

B

C

D

16.

A

B

C

D

7.

A

B

C

D

17.

A

B

C

D

8.

A

B

C

D

18.

A

B

C

D

9.

A

B

C

D

19.

A

B

C

D

10.

A

B

C

D

20.

A

B

C

D

Your final mark Section A = _____ 20

Total score = _____ 94

Section B = _____ 74

Percentage (%) =

Unit Two Chemistry 2017 Section B – Short Answers In this section you need to write your answers to each question in the spaces provided. You must answer every question. You must show all the appropriate working out for questions that require mathematical calculations. Marks will be deducted for incorrect use of units and significant figures.

Question 1 Write equations to show the following compounds dissolving in water. States of matter must be shown. a.

CH3COOH (l) (ionisation)

___________________________________________________________________________________ b.

C2H5OH (l)

___________________________________________________________________________________ c.

(NH4)2SO4 (s)

___________________________________________________________________________________ 6 marks Question 2 Write balanced equations for the following. You must show the states of matter. a.

Sodium metal and hydrochloric acid

___________________________________________________________________________________ b.

Sodium hydroxide and sulfuric acid

___________________________________________________________________________________ c.

Solid magnesium carbonate and hydrochloric acid

___________________________________________________________________________________ 6 marks

Unit Two Chemistry 2017 Question 3 Consider the molecules labeled A and B below. A

B

Which molecule, A or B, will have the greater solubility in water? You must support your answer with an explanation. ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 2 marks Question 4 Convert the following concentrations into the units shown in the brackets. a.

1.0 M HCl (mg/L)

___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 2 marks

Unit Two Chemistry 2017

b.

2.1 mol L-1 CuSO4 (% w/v)

___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 2 marks c.

2.1 % w/v CuSO4 (mol/L)

___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 2 marks Question 5 What is the mass of Chlorine in 20.0 mL of 0.25 M BaCl2? ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________

Unit Two Chemistry 2017 3 marks Question 6 What is the concentration of the resultant solution formed when 15.0 mL of 0.10 M H 2SO4 is diluted with 100 mL of water? ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 2 marks Question 7 Hydrogen sulfide gas, H2S, burns in oxygen to produce water and sulfur dioxide according to the equation: 2H2S(g) + 3O2(g)  2H2O(g) + 2SO2(g) What mass of oxygen gas would be required to produce 6.4 g of sulfur dioxide? ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 2 marks Question 8 25.0 g of methanol (CH3OH) reacts with 35.0 g of oxygen according to the reaction: 2CH3OH(g) + 3O2(g)  2CO2(g) + 4H2O(l) a.

Which reactant is in excess? Determine the mass of this excess reactant that is left unreacted.

___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 3 marks

Unit Two Chemistry 2017

b.

What is the mass of CO2 produced?

___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 2 marks Question 9 A student wishes to perform a titration to determine the concentration of an unknown solution of hydrochloric acid. She uses a standard solution of 0.10 M sodium hydroxide. She fills a burette with the standard solution. A 10 mL sample of the unknown solution is pipetted into a 250 mL volumetric flask which is filled up to the calibration mark with distilled water. From this diluted solution a 25.0 mL aliquot is transferred into a 100 mL conical flask. 3 drops of phenolphthalein are placed into the flask. The student performs 4 titrations and records the results in the table below: 1st titre 9.8 mL a.

2nd titre 10.1 mL

3rd titre 9.9 mL

4th titre 10.9 mL

What is the function of the phenolphthalein?

___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 2 marks b.

What is the average of the concordant titres?

___________________________________________________________________________________ 1 mark c.

Calculate the number of moles of NaOH that reacted with the DILUTED 25.0 mL of unknown solution.

___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 2 marks

Unit Two Chemistry 2017

d.

Calculate the concentration (molarity) of the unknown solution (undiluted) of hydrochloric acid. The equation for the reaction between HCl and NaOH is NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l)

___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 3 marks e.

Would the calculated molarity of HCl in the unknown solution be higher or lower than the true value if the burette was rinsed out with water. Give an explanation for your answer.

___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 2 marks f.

With what solution should the following pieces of glassware have been rinsed with prior (before) to the titration? i.

10 mL pipette ____________________________________________________________

ii.

250 mL volumetric flask ____________________________________________________

iii.

25 mL pipette ____________________________________________________________

iv.

Conical flask _____________________________________________________________ 4 marks

Unit Two Chemistry 2017

Question 10 A green leaf with a mass of 0.32 g is analysed for its chlorophyll content by uv-visible spectroscopy. The chlorophyll from the leaf is extracted and allowed to dissolve in 250 mL of solvent. A small sample of the chlorophyll solution is placed in a uv-visible spectrometer that has the wavelength selector set at 410 nm. The absorbance of the chlorophyll solution at this wavelength is 0.21. The absorbance values of...