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AQA A Level Chemistry > Chapter 9 + 10 : Group 2 and 7 elements > Flashcards

Chapter 9 + 10 : Group 2 and 7 elements Flashcards

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1
Q

Explain the trend in atomic radius in group 2?

A

Atomic radius increases down the group due to the extra electron shells

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2
Q

Explain the trend in the first ionisation energy of group 2?

A

The first ionisation energy decreases down the group due to the shielding from the nucleus the extra inner shell of electrons provide. The extra shell also increases the distance between the nucleus and the outer shell of electrons reducing the nucelus’ attraction.

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3
Q

Why does the melting point of group 2 elements decrease down the group?

A

The atomic radius increases in size so the two delocalised electrons will be further from the attraction of the nucelus, meaning less energy is required to break the bonds and thus have a lower melting point.

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4
Q

At which point in group 2 is there an anomaly in melting points and explain why?

A

Magnesium, as the crystal structure/ arrangement of of metallic ions changes.

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5
Q

Group 2 metal + water = ?, how readily do they react?

A

metal hydroxide and hydrogen. They react more readily down the group due to the decreasing ionisation energies.

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6
Q

Describe the trend in solubilty of group 2 compounds?

A

Elements containing a singly charged negative ion (OH-) increase in solubilty down the group whearas doubly charged negative ions (SO42-) decrease in solubilty.

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7
Q

What is the correct term for substances with very low solubilities?

A

Sparingly soluble

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8
Q

How do you test for sulfate ions?

A

Add BaCl2 (barium chloride), if sulfate ions are present a white precipitate of barium sulfate will form

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9
Q

What can group 2 compounds be used for in relation to their ability to neutralise acids?

A

Calcium hydroxide, slaked lime is used in agriculture to neuralise acid soils.
Magnesium hydroxide can be used as an antacid as an indegestion remedy to neutralise stomach cids.

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10
Q

State a use of barium sulfate?

A

Barium meal, barium sulfate is opaque on x-rays and so can be used to help diagnose problems with the oesophagus, stomach or intenstines. A patient swallows the barium meal which the coats their organs

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11
Q

Describe the process of extracting titanium from it’s core?

A

TiO2 is converted into TiCl4 by heating it with carbon in a stream of carbon gas.
TiCl4 then purified using fractional distillation before being reduced by magnesium in a furnance at almost 1000 degrees

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12
Q

Write the equation for the extraction of titanium from it’s core?

A

TiCl4 (g) + 2Mg (l) = Ti (s) + 2MgCl2 (l)

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13
Q

How can group 2 compounds be used to remove pollutants?

A

Burning fossil fuels to produce electricity an produce sulfur dioxide, a pollutant.
Sulfur dioxide can be removed from flue gases by reacting with powdered CaO (lime) and CaCO3 (limestone).
A slurry is then made by mixing the CaO or CaCO3 with water, it is then sprayed onto the flue gases. The alkaline then reacts with the sulfur dioxide and produces teh solide waste products calcium sulfite.

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14
Q

What colours and physical states are the halogens?

A

Fluorine- Pale yellow gas
Chlorine- Green gas
Bromine- Red/Brown liquid
Iodine- Grey solid

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15
Q

Describe and explain the trend of the electronegativity of group 7?

A

Electronegativity decreases down the group as the atoms get larger down the group and so the electrons are further from the nucleus and are shielded by more electrons so experience less attraction from the nucelus.

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16
Q

Describe and explain the trend in boiling points of group 7?

A

Boiling point increases down the group due to the increasing strength of the van der waals forces as the size and mass of the elements increase. The trend is highlighted by the change in physical state at room temperature.

17
Q

How do the halogens react with halide ions?

A

Halogens displace less reactive halide ions from solution, the halogens get less recative down the group due their increase in size.

18
Q

Cl2 + KBr = ?

A

2 KCl + Br2 (orange solution)

19
Q

CL2 + KI = ?

A

2 KCL + I2 (brown solution)

20
Q

Br2 + KI = ?

A

2 KBR + I2 (brown solution)

21
Q

Write the equation for the production of bleach?

A

Cl2 + 2 NaOH = NaClO + NaCL + H2O

22
Q

What uses are there of NaCLO?

A

Bleach- water treatment, bleaching paper and textiles, cleaning

23
Q

Write the ionic equation for the reaction of chlorine and sunlight?

A

2 Cl2 + 2 H2O = 4 H+ + 4 Cl- + O2

24
Q

Write the ionic equation for the reaction of chlorine and water, what does it undergo?

A

Cl2 + H2O + 2 H+ + Cl- + ClO-

Disproportionation

25
Q

What are the positives of chlorine water treatment?

A

Kills disease causing microorgansims
Prevents reinfection further down in the supply as some chlorine persists
Prevents growth of alagae, eliminating bad tastes and smells and removes discolouration

26
Q

What are the negatives of chlorine water treatment?

A

Chlorine gas is very dangerous if inhaled, and liquid chlorine can cause severe chemical burns.
Chlorine can react with organic compounds and from chlorinated hydrocarbons which can be carcinogenic.

27
Q

Describe and explain the reducing power/reactivity of the halide ions?

A

Increases down the group as the attraction between the nucleus and the outer electrons gets weaker as the ions get bigger and there is a shielding effect.

28
Q

Describe the test for the halide ions?

A 
Add dilute nitric acid to remove any ions.Add AgNO3, a precipitate will form. 
F = no  ppt
Cl = White ppt
Br = cream ppt
I = yellow ppt.
Then add NH3:
29
Q

Describe the test for the halide ions?

A 
Add dilute nitric acid to remove any ions.Add AgNO3, a precipitate will form. 
F = no  ppt
Cl = White ppt
Br = cream ppt
I = yellow ppt.
Then add NH3: 
Cl = dissolves in dilute
Br = dissolves in concentrated
I = insoluble in concentrated
30
Q

Explain how you would conduct a flame test?

A

Dip a nichrome wire loop into concentrated HCL
Then dip the wire loop into the sample
Hold the loop in the clear blue flame of the bunsen burner.
Observe the colour change

31
Q

What is the the test for ammonium ions?

A

Ammonia gas is alkaline so when a damp piece of red litmus paper is dipped in the test tube it will turn blue.
Add hydroxide ions to a solution containing amonium ions and ammonia and water will be produced. To test for amonium ions in solution add dilute NaOH and gently heat, if positive ammonia will be given off as a gas

32
Q

How do you test for sulphate ions?

A

Add HCL, then BaCl2, if a white ppt of barium sulafte is formed, sulfate ions are present

33
Q

How do you test for hydroxides?

A

Dip red litmus paper into soluton, if OH- ions are present it will turn blue

34
Q

How do you test for carbonates?

A

Add HCL = fizzing

Use limewater to test for CO2 = cloudy

35
Q

What colours do group 2 ions produce in a flame test?

A 
Ca2+ = brick red
Sr2+ = red
Ba2+ = pale green

AQA A Level Chemistry (10 decks)

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