Groups 2, 7 And Redox Flashcards
Hydrazoic acid has the formula HN3. The oxidation state of nitrogen in hydrazoic acid is:
A) 0
B) -1
C) +3
D) -1/3
D ✔️
Which of the following could no be an element in group 2?
A) an element with an oxide which forms a solution of pH 10
B) an element with an insoluble sulphate
C) an element with a chloride which is liquid at RTP
D) an element with a carbonate which decomposes on heating
C ✔️
Explain the reactivity trend of group 2.
Gets more reactive as you do down the group ✔️
When group 2 elements react with oxygen, what forms and give an example with an equation of O and Mg. Also write which elements are oxidised and reduced.
Include state symbols.
They react to form metal oxides.
2Mg(s) + O2(g) —> 2MgO(s)
0 +2 Oxidation
0 -2 Reduction
✔️
Explain what happens when group 2 reacts with water. Write an equation using Sr as an example, also include which elements are oxidised and reduced.
Include state symbols.
Group 2 react with water to form an alkaline hydroxide and hydrogen gas.
Sr(s) +2H2O(l) —> Sr(OH)2(aq) + H2(g)
0 +2
+1 0
Sr is oxidised
H is reduced ✔️
Write the reaction between Magnesium and Hydrochloric acid including state symbols. Note the redox for H and Mg.
Mg(s) + 2HCl(aq) —> MgCl2(aq) + H2(g)
0 +2
+1 0
Mg is oxidised
H is reduced ✔️
Write the first 3 ionisation energies of Ca.
Ca(g) —> Ca+(g) + e-
Ca+(g) —> Ca2+(g) + e-
Ca2+(g) —> Ca3+(g) + e-
✔️
Why do group 2 elements sometimes be referred as “redusing agents”?
They reduce the another species in an equation. ✔️ (add e- to the other species)
A)Write the reaction of Calcium oxide with water. What pH is the solution after the reaction? *(include state symbols and charges of any ions)
B)Group 2 metals are onto slightly soluble in water, write the equation for when the product of the previous reaction becomes saturated.
A) CaO(s) + H2O(l) —> Ca2+(aq) + 2OH-(aq)
The solution becomes alkaline.
B) Ca2+(aq) + 2OH-(aq) —> Ca(OH)2(s)
✔️
What’s the trends in group 2 hydroxides as you go down the group for these:
A) solubility
B) pH
C) alkalinity
A) solubility increases
B) pH increases
C) alkalinity increases ✔️
Why are group 2 used as bases?
They have the ability to neutralise acids.✔️
How are group 2 compounds used in medicine?
Antacids for treaties indigestion ✔️
What would be the colour of the solution when iodine is dissolved in a hydrocarbon solvent?
Purple ✔️ hydrocarbons are organic
Which of the following statements about the elements in group 7 is incorrect?
A) they all show variable oxidation states in their compounds
B) they all form acidic hydrides
C) electronegativity decreases as the group is descended
D) they all exist as diatomic molecules
A ✔️
What is a disproportionation reaction?
It’s a redox reaction which the same element is both oxidised and reduced✔️
A student discovered that the sea water contains chloride ions. The student added aqueous silver nitrate to a sample of sea water.
- What would the student see?
- Write an ionic equation (inc state symbols) for the reaction that would occur.
- State one benefit of adding Cl2 to water.
- Suggest one hazard of adding Cl2 to drinking water.
- A precipitate would form.
- Cl-(aq) + Ag+(aq) —> AgCl(s)
- Kills bacteria / sterilises water
- Chlorine is cancer causing when combined to hydrocarbons. ✔️
Complete the table:
HALOGEN DISPLACEMENT
•Include colour formation and equation of reaction
Halogen | Cl2(aq) | Br2(aq) | I2(aq) |
——————————————————————
Cl-(aq) | ///////// | A | B |
——————————————————————
Br-(aq) | C | ////////// | D |
——————————————————————
I-(aq) | E | F | ///////// |
A) no reaction
B) no reaction
C) Orange colour formed
Cl2(aq) + 2Br-(aq) —> 2Cl-(aq) + Br2(aq)
D) no reaction
E) Violet colour formed
Cl2(aq) + 2I-(aq) —> 2Cl-(aq) + I2(aq)
F) Violet colour formed
Br2(aq) + 2I-(aq) —> 2Br-(aq) + I2(aq)
✔️✔️✔️
Explain what you see when:
A) Cl2 + water
B) Br2 + water
C) Br2 + cyclohexane (top layer of colour)
D) I2 + cyclohexane (top layer of colour)
E) Cl2 + cyclohexane (top layer of colour)
F) I2 + water
A) pale green B) orange C) orange D) violet E) pale green F) brown ✔️
State the trends in the halogens for: • electrons • London forces • energy required to break IM forces • boiling point
- more electrons (lols)
- stronger London forces
- more energy required to break IM forces
- boiling point increases ✔️
The equation for the reaction of Cl2 and water is shown below:
Cl2(g) + H2O(l) > HCl(aq) + HClO(aq)
- State the oxidation number of Cl in”
a) Cl2 b) HCl c) HClO - Why is the reaction a disproportionation reaction? (Explain using the numbers in Q.1)
- Cl2 reacts with NaOH to form bleach in another reaction.
Write an equation for this reaction.
- a) 0 b) -1 c) +1
- Chlorine is both oxidised and reduced during the reaction, oxidised when it’s in HCl and reduced when it’s in HClO.
- Cl2 + 2NaOH —> ClO + NaCl + H2O
Group 2 elements also react with dilute HCl.
Describe and explain the trend in reactivity of the group 2 elements with dilute HCl as the group descended.
- increases size of radii
- more shielding
- attraction from nucleus decreases outweighing nuclear charge
- reactivity increases
Complete the table:
•Halide tests using Ag+(aq).
| Ionic | colour of | solubility Halide | equation | precipitate |NH3(aq) —————————————————————— Cl- | A | Aa | Aaa —————————————————————— Br- | B | Bb | Bbb —————————————————————— I- | C | Cc | Ccc
A) Ag+(aq) + Cl-(aq) -> AgCl(s) Aa) White Aaa) soluble in dilute NH3(aq) B) Ag+(aq) + Br-(aq) -> AgBr(s) Bb) cream Bbb) soluble in conc. NH3(aq) C) Ag+(aq) + I-(aq) -> AgI(s) Cc) yellow Ccc) insoluble in conc. NH3(aq) ✔️
What’s the carbonate test and what’s it for?
• you add dilute acid to a solution
• if there is fizzing of CO2 gas the solution is contaminated as neither sulphate nor halide ions produce bubbles with dilute acid.
• is there is no fizzing then no carbonate is present and you can proceed to the next test
✔️
Explain the sulphate test.
- you add a solution containing Ba2+(aq) ions
* you’re looking for a white precipitate of BaSO4(s) ✔️
What’s the halide test?
When you add a solution containing Ag+(aq) ions and are looking for a precipitate.
✔️
Put these tests in the correct order and explain why they need to be in this order.
- sulphate test
- carbonate test
- halide test
Order:
• carbonate, sulphate and halide.
It needs to be in this order bc the sulphate test reacts to carbonate ions, therefore it will give a false positive if the carbonate test wasn’t done before. Also the halide test needs to be last bc Ag+ ions react with carbonates and sulphates to create precipitates and therefore giving a false positive again. ✔️✔️
