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Group 7 OCR Chemistry AS/A level detailed summary notes/class notes £2.99
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Group 7 OCR Chemistry AS/A level detailed summary notes/class notes

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This compartmentalised document contains complete, thorough notes on the halogens (Group 7) and can also act as a "test yourself" resource by covering up certain parts. I use exam vocabulary in my document but it's still easy to follow. These notes are arranged in bullet points, making it clear whe...

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  • January 14, 2022
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  • 2021/2022
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Available practice questions

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Some examples from this set of practice questions

1.

A student adds a small volume of aqueous silver nitrate to an aqueous solution of bromide ions in a test-tube. The student then adds a similar volume of dilute aqueous ammonia to the same test-tube. Describe what the student would see in the test-tube after the addition of aqueous ammonia.

Answer: A cream precipitate would form.

2.

Chlorine reacts with aqueous sodium hydroxide to form bleach. Write the equation and state the conditions for this reaction. Include the conditions.

Answer: Equation 2NaOH + Cl2  NaCl + NaClO + H2O  Conditions cold AND dilute (sodium hydroxide)

3.

The student is provided with an aqueous solution of calcium bromide that is contaminated with calcium iodide. The student carries out a chemical test with silver ions but this time needs to add a second reagent to show that iodide ions are present. State the second reagent that the student would need to add.

Answer: concentrated (aqueous) NH3

4.

In drinking water, HClO kills bacteria. Write an equation to show how HClO can form in drinking water

Answer: Cl2 + H2O  HClO + HCl

5.

Some scientists believe that chlorine compounds should not be present in drinking water. Suggest one reason why scientists may be worried by the presence of these compounds.

Answer: Chlorine compounds are carcinogenic Chlorine compounds are toxic/ poisonous

The halogens
Physical properties:
Þ the halogens are diatomic



Element State Colour Colour of vapour
I 2

Fluorine Gas Pale yellow -

Chlorine Gas Green -

Bromine Liquid Brown Brown

Iodine Solid Grey Purple




Reactivity:
Þ The halogens react by gaining an electron to form 1– Melting
halide ions
Reactivit point
Þ Reactivity decreases down the group because: y
* Atomic radius increases down the group

* The number of electrons increases down
the group

* The number of shells increases down the
Þ This decreases
group the attraction of the nucleus towards electrons due

to electron shielding and the outer shell being further from the nucleus




Melting/Boiling points:
Þ Melting/boiling is caused by intermolecular forces being overcome
by thermal energy

Þ Melting/boiling points increase going down the group because:
* The number of electrons increases down the
group

* Thisthermal
Þ More makes energy
the induced
is dipole-dipole forces
needed to overcome these

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