Group 7 and Redox Flashcards by MARY Fasina

Describe fluorine

-yellow gas
-very reactive
-toxic

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Describe chlorine

-green gas
-very reactive
-toxic

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Describe bromine

-orange liquid
-very reactive
-toxic
-often used as a solution in water-bromine water, Br2(aq)

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Describe iodine

-grey crystals
-reactive
-toxic
-easily turns into purple vapour on heating
-used in solution as an antiseptic

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What colour is iodine solution?

Brown

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Describe the trend in atomic radius of group 7 down the group

-atomic radius increase
-because more shells/more shielding
-so bigger atoms

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What is electronegativity?

-the power of an atom to attract the 2 electrons in a covalent bond

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Describe the trend in electronegativity down group 7

-electronegativity increases
-bigger atoms/ more shells
-more shielding
-weaker attraction between buckeye and 2 electrons in covalent bond

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Describe the trend in melting/ boiling points down group 7

-bigger molecules
-more electrons
-stronger van der waals forces between molecules
-higher mpt/bpt

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Describe the trend in 1st ionisation energy down group 7

-1st IE decreases
-atoms get bigger/ more shells
-more shielding
-therefore weaker attraction from nucleus to electron in outer shell

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What happens to reactivity going down group 7?

Reactivity decreases because it becomes more difficult to gain an e-
The trend in reactivity enables the halogens to undergo displacement reactions

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What happens in the reaction: Cl2(aq) + 2KI(aq) —> I2(aq) + 2KCl(aq)

-Here, a more reactive halogen replaces a less reactive halogen in a halide salt compound
-Chloride had been reduced
-Iodide has been oxidised
-Potassium is a spectator ion

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What happens in the reaction between bromine and chloride

no reaction

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What gained in the reaction between iodine and chloride

no reaction

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What happens in the reaction between chlorine and bromide

yellow solution forms

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What is the ionic equation for the reaction between chlorine and bromide

Cl2 + 2Br- —> 2Cl- + Br2

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What happens in the reaction between iodine and bromide

no reaction

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What happens in the reaction between chlorine and iodide

brown solution forms

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What is the ionic equation for the reaction between chlorine and iodide

Cl2 + 2I- —> 2Cl- + I2

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What happens in the reaction between bromine and iodide

brown solution forms

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What is the ionic equation for the reaction between bromine and iodide

Br2 + 2I- —> 2Br- + I2

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Put chlorine iodine and bromine in order of strongest to weakest oxidising power

strongest—chlorine, bromine, iodine—weakest

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Explain the order of oxidising power from chlorine(chlorine) to iodine(weakest)

-Halogen atom gains an electron when it oxidises the halide ion
-The smaller the halogen atom, the easier it is to gain an electron as it is smaller and has less shielding

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What is an oxidising agent

Oxidising agents accept electrons
Therefore oxidising agents are reduced

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What are reducing agents

Reducing agents are electron donors Therefore, reducing agents are oxidised

In the reaction: 2Mg + O2 —>2MgO , what is the oxidising agent and what is the reducing agent?

Mg- reducing agent O2- oxidising agent

When writing half equations, where do the electrons go for a reduction reaction and a oxidation reaction

reduction- left oxidation- right

What are oxidation states

Oxidation states are a method for working out if a substance is oxidised or reduced. Every element in a compound is given an oxidation number. Changes in oxidation number indicate if oxidation or reduction is happening

What oxidation number do elements have and why?

0 Because they haven’t lost or gained any electrons

In a simple ion, what is the oxidation number of each element the same as?

it’s charge

What is the overall oxidation number for the uncharged ionic substance? Give examples

0 -NaCl—> Na Ox= +1; Cl Ox=. -1

How do we assign oxidation numbers to covalent molecules

The same way as if they were ionic

What are the general rules for oxidation numbers ?

What is the oxidation number of S in SO4 2-

Oxygen ion is -2 -2 x 4 ‎ = -8 The total has to be -2, so the oxidation number of S has to be 6 because -8 + 6= -2

What is the oxidation number of Cr in Cr2O7 2-

Oxygen ion is -2 -2 x 7 ‎ = -14 The total number has to be -2, so the oxidation number of Cr2 is 12. Therefore, the oxidation number of Cr is 6

What are the oxidation numbers of Na and H in NaH?

Usually H is +1, however since it’s joined with a metal, on this occasion, it is -1 And Na is +1

What are the oxidation numbers of H and O in H2O2?

What is one key thing that must be remembered when writing half equations?

all reactants and products must be balanced

What are the steps to ensure that half equations are balanced

-atoms -ions -charges -electrons (in this order)

Write a half equation for chlorine gas being reduced

How can we tell if a reaction is an oxidation or reduction?

If the change in oxidation number goes down, it is a reduction and if it goes up, it is an oxidation

What are the rules for constructing half equations

You are only allowed to write certain things in half equations: -the substance you start from snd what it is oxidised or reduced to. -Hydrogen ions -Water -Electrons (in this order)

Write a half equation for SO4 2- —> S

First try to balance: Add a 4H20 on the side of the products and a 8H+ on the side of the reactants. Then calculate the change in oxidation number. The Ox of S in SO4 2- is +6 and the Ox of S is 0 so therefore the Ox has gone down which means the reaction is a reduction snd the number of electrons needs to go on the left. 6e- + 8H+ + SO4 2- —> S + 4H2O

Write a half equation for IO3- —> I2

First try to balance: Add a 2 in front of IO3-, a 6H2O on the side of the products and a 12H+ on the side of the reactants. Then calculate the change in oxidation number +5–>0 +5–>0 The number goes down so the reaction is a reduction reaction and the electrons go on the left. 12H+ + 2IO3- + 10e- —> I2 + 6H2O

Write a half equation for VO^2+ —>VO2+

First try to balance: Add a H2O to the side of the reactants and a 2H+ to the side of the products Then calculate the change in oxidation number +4—>+5 The oxidation number is going up, therefore the reaction is an oxidation reaction and the electrons need to go on the right hand side H2O + VO^2+ —> VO2+ + 2H+ + e-

Write a half equation for the oxidation of sodium metal to sodium 1+ ion and write a half equation for the reduction of fluorine gas to fluoride ions. Then combine the equation.

1)Na —> Na+ + e- 2)F2 + 2e- —> 2F- Then multiply equation 1 by 2 dk that there the same number of electrons in both the oxidation reaction reduction reaction and combine them. 2Na —> 2Na+ + 2e- 2Na + F2 —> 2Na+ + 2F-

Between fluorine, chlorine, bromine and iodine, which one has the highest reducing power and why?

Iodine Because it has the most shells, most shielding, its the largest ion and has the lowest charge density

When a halide ion acts as a reducing agent, what does it do?

It loses electrons

What type of reaction happens with a chloride ion (NaCl) and sulfuric acid(H2SO4)?

displacement

What is the product from the reaction between NaCl and H2SO4 and what are the observations?

HCl Steamy fumes

What is the equation for the reaction between NaCl and H2SO4?

NaCl + H2SO4 -> NaHSO4 + HCl

What type of reaction happens between NaBr and H2SO4?

Displacement

What is the product formed from the reaction between NaBr and H2SO4 and what are the observations?

HBr Steamy fumes

What is the equation for the reaction between NaBr and H2SO4?

NaBr + H2SO4 -> NaHSO4 + HBr

What type of reaction is the reaction between Br- and H2SO4?

Redox

What is the product made in the reaction made between 2Br- , 2H- and H2SO4 and what are the observations?

Br2 Brown fumes

What is the equation for the reaction between Br- and H2SO4?

2Br- + H2SO4 + 2H- -> Br2 + SO2 + 2H2O

What type of reaction is the reaction between Br- and H2SO4?

redox

What is the name of the product between the Br- and H2SO4 and what are the observations?

SO2 colourless gas

What is the name of the reaction between NaI and H2SO4?

displacement

What is the name of the product formed in the reaction between NaI and H2SO4 and what are the observations?

HI steamy fumes

What is the equation for the reaction between NaI and H2SO4?

NaI + H2SO4 —> NaHSO4 + HI

What type of reaction is the reaction between I-, H+ and H2SO4?

redox

What are the products made in the reaction between I-, H+ and H2SO4 and what are the observations?

I2 purple fumes

What is the equation between I- , H+ and H2SO4?

2I- + H2SO4 + 2H- —> I2 + SO2 + 2H2O

What type of reaction is the relaxation between I- and H2SO4?

redox

What type of reaction is the reaction between 6I-, H2SO4 and 6H-?

redox

Group 7 and Redox Flashcards

(70 cards)