The halogens exist as diatomic molecules, X2.
Descending through Group 17 from chlorine to iodine the boiling points of the elements increase.
Which statement explains this trend?
Of the permanent dipole in the X2 molecule increases as the group is descended.
The X–X bond strength increases as the group is descended.
the electronegativity of X decreases as the group is descended.
The number of electrons in each X2 molecule increases as the group is descended.
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How do the strengths of the forces between molecules, and the bonds within molecules, vary going down Group 17 from chlorine to bromine to iodine?
|
Strength of van der Waals’ forces |
Strength of covalent bonds |
|
|
A B C D |
Increase Decrease Increase Decrease |
Increase Increase Decrease Decrease |
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A scientist compares the properties of chlorine, iodine and their compounds.
Property X for iodine is bigger than for chlorine.
What is property X?
Solubility of the silver halide in NH3 (aq)
Oxidising ability of the element
Thermal stability of the hydrogen halide
Strength of van der Waals’ forces between the molecules of the element
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Which properties of hydrogen halides steadily increase in the sequence HCl, HBr and HI?
|
1 |
Bond length |
|
2 |
Ease of oxidation |
|
3 |
Thermal stability |
1 only
1 and 2
2 and 3
1, 2 and 3
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The following report appeared in a newspaper:
| Barrels of bromine broke open after a vehicle collision on the motorway. Traffic was diverted as purple gaseous bromine drifted over the surface of the road (as bromine is more dense than air), causing irritation to drivers’ eyes. Firemen sprayed water over the scene of the accident, dissolving the bromine and washing it away. |
Which of the following observations is incorrect in the report?
Bromine is not purple
Bromine does not vaporise readily
Bromine is not denser than air
Bromine does not dissolve in water
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A molecule of chlorine has a relative molecular mass of 72.
Which properties of the atoms in this molecule are the same?
|
1 |
Radius |
|
2 |
Relative isotopic mass |
|
3 |
Nucleon number |
1 only
1 and 2
2 and 3
1, 2 and 3
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Which graph correctly illustrates a trend found in the halogen group?
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Which statement about Group 7 elements is not correct?
Fluorine is the weakest reducing agent in Group 7.
The bond dissociation energy of the hydrogen halides from HCl to HI increases.
CH3I would produce a silver halide precipitate with acidified AgNO3 faster than CH3Cl or CH3Br.
Astatine has a lower first ionisation energy than iodine.
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Hydrogen halides, H-X, are formed from the reaction of hydrogen and a halogen, X2. Which of the following statements correctly explains why HBr (aq) is a stronger acid than HF (aq)?
HF (aq) releases more H+ ions
HF dissociates more readily than HBr when dissolved in solution
The H-Br bond has the greatest bond dissociation energy
The H-F bond is stronger so does not break as easily
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Shown on the graph are the relative values of the first ionisation energies of four elements that have consecutive atomic numbers. One of the elements reacts with hydrogen to form a covalent compound with formula HX.
Which element could be X?
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