ELEMENTS FROM THE SEA

What is the charge of a group 5 ion?

-3

What does NaCl (aqueous) mean?

The Na+ and Cl- are completely separate. The ions are surround by water molecules held by ion-dipole forces.

Formula for hydrogen sulfate ion

HSO4-

Formula for hydrogen carbonate ion

HCO3-

Formula for nitrate ion

NO3-

Formula for nitrite ion

NO2-

Formula for sulfate ion

SO4 2-

Formula for sulfite ion

SO3 2-

Formula for ammonium ion

NH4+

Formula for chromate ion

CrO4 2-

Formula for dichromate ion

Cr2O7 2-

Formula for peroxide ion

O2 2-

Formula for cyanide ion

CN-

Formula for phosphate ion

PO4 3-

Formula for permanganate ion

MnO4-

What is the name of ions that do not take part in a reaction?

Spectator ions

Name the 4 common spectator ion

NO3- / SO4 2- / Na+ / K+

What is a spectator ion?

Ions that do not take part in a reaction

What is a precipitate?

A solid held suspended in a liquid. Formed when 2 ionic solutions are mixed and a double displacement reaction occurs

What is a positively charged ion?

A cation

What is a negatively charged ion?

An anion

Flame colour of Li+

Crimson

Flame colour of Na+

Orange-yellow

Flame colour of K+

Lilac

Flame colour of Ca2+

Brick-red

Flame colour of Ba2+

Green

Flame colour of Cu2+

Blue-green

Describe the test for halides

Add dilute nitric acid, then silver nitrate solution.

How to distinguish between silver halide precipitates?

Add dilute ammonia (NH3) / AgCl dissolves / AgBr partially dissolves / AgI dont dissolve.

Precipitate test for Fe2+ ion (include test result)

Add NaOH, green precipitate forms

Precipitate test for Fe3+ ion (include test result)

Add NaOH, brown precipitate forms

Precipitate test for Cu2+ ion (include test result)

Add NaOH, blue precipitate forms

Test for sulphates (include test results)

Add dilute HCl and barium chloride, white precipitate forms

Test for hydroxide ions (include test results)

Dip red litmus paper into solution, if hydroxide ion is present then the paper will turn blue.

Test for ammonia gas (NH3)

Expose ammonia gas to a piece of damp red litmus paper. If ammonia is present, paper will turn blue.

Test for ammonium ion (NH4+)

NH4+ + OH- —> NH3 + H2O. Then test for ammonia gas

Test for iodide ion (without AgNO3)

Add Pb(NO3)2, bright yellow precipitate forms

What happens to O.S during oxidation

O.S becomes more positive

What happens to O.S during reduction

O.S becomes more negative

What happens to the electrons / oxygen / hydrogen during oxidation?

Electrons are lost / oxygen is gained / hydrogen is lost

What happens to the electrons / oxygen / hydrogen during reduction

Electrons are gained / oxygen is lost / hydrogen is gained

O.S of fluorine is always…

-1

O.S of elements are always…

0

Cl in covalent compounds are usually…

-1

What is the colour of Br2 in water?

Orange

What is the colour of Cl2 in water?

V.pale green / colourless

What is the colour of I2 (iodine) in water?

Orange-brown

What is the colour of F2 (fluorine) in water?

N/A

What is the colour of Br2 in organic solvent?

Orange

What is the colour of Cl2 in organic solvent?

Colourless

What is the colour of I2 (iodine) in organic solvent?

Purple

What is the colour / state of Br2 at RTP?

Liquid / red-brown

What is the colour / state of Cl2 at RTP?

Gas / v.pale green

What is the colour / state of I2 (iodine) at RTP?

Solid / grey-black

Describe a test for displacement reaction between a halogen and halide ion

1cm³ of halogen + 1cm³ of halide solution, shake, + 1cm³ of cyclohexane, shake well

Systematic name for SO4 2-

Sulphate (VI) ion

Systematic name for N2O

Nitrogen (I) oxide

Systematic name for FeCl2

Iron (II) chloride

Systematic name for Mn(OH)2

Manganese (II) hydroxide

Which electrode does oxidation occurs?

The anode

Which electrode does reduction occur?

The cathode

Whats the equation for the oxidation of H2O?

H₂O —> ½ O₂ + 2e^- + 2H⁺

Whats the equation for the reduction of H2O?

H₂O + e^- —> ½ H₂ + OH^-

What can be oxidised at the anode during aqueous electrolysis?

Either halide ions OR H2O

What can be reduced at the cathode during aqueous electrolysis?

Either group 3 / transition metal ions OR H2O

What electrolyte is used during the purification of copper?

CuSO4 (aq) solution (blue)

What is the anode made of? (purification of copper)

Impure copper

What is the cathode made of? (purification of copper)

Pure copper

What happen at the anode? (purification of copper)

Impurities fall / mass decreases

What happens at the cathode? (purification of copper)

Mass of cathode increases as Cu (s) is formed

Equation at the anode (purification of copper)

Cu —> Cu2+ + 2e-

Equation at the cathode (purification of copper)

Cu2+ + 2e- —> Cu (s)

Equation for atom economy (using Mr)

(Mr of useful products / Mr of all reactant) x 100

How can you get 100% atom economy?

All products are useful / if only one product is made (addition rxns) / rearrangement rxns

Equation for %yield

(Actual mass of products / max possible mass of products) x 100

(Main) reasons for a low yield (2)

Transfer losses / reaction may not have gone to completion

Reason for a yield over 100% (1)

Solid (usually organic) may be wet

Explain, in terms of electrons, why a bromine atom is more reactive than an iodine atom

Bromine attracts electrons more (strongly) than iodide

Explain which of chloromethane and bromomethane would undergo hydrolysis more rapidly

Bromomethane, the C-Br bond enthalpy is lower / weaker than the C-Cl bond

What bonds do hydrogen halides have?

Covalent

What does HX (g) in water make?

Acid (solution)

Equation for % yield:

(Actual mass / theoretical mass) x 100

What are the main 2 reasons for low yield?

Transfer losses / Reaction may not have gone to completion

What are the main reasons for yield over 100%

Solid may be wet

What does volatility mean (in halogens)?

How easily something becomes a gas

What is the trend in volatility of the halogens? + give a short reason

Decreases down the group as IMF gets stronger

What are the (2) importance of chlorine

To extract Br2 from seawater / to make bleach, to treat water as it kills bacteria

Which halogen is the best oxidising agent?

F2 is the best as smallest atoms, therefore strongest force of attraction

What are the 3 reactions of halogens? (bullet point it)

1. Halogen + halide

2. Halogen + alkene

3. Halogen + alkane

What type of reaction is halogen + alkane?

Radical substitution

What type of reaction occurs when u heat hydrogen halides?

Thermal decomposition

Write an balanced equation of what happens when you heat HX (hydrogen halide)

2HX → H2 + X2

Which hydrogen halide is the easiest to decompose? (just state)

HI

What is the trend of thermal stability of hydrogen halides?

Decreases down the group

Why is H-I the weakest covalent bond in comparison to other hydrogen halides?

Iodine is the largest halogen atom / the shared e- are further from the nucleus

Charge density is only valid for what type of particle?

Ions

What molecule is used to test for HX (g)? (include state symbols)

NH3(g)

What are the observations of heating HBr? and why?

Orange-brown gas / Br(g) produced

What are the observations of heating HI? and why?

Purple gas / I2(g) produced

What is the general equation for MAKING hydrogen halides? include state symbols

NaX(s) + c.H2SO4(aq) → NaHSO4(aq) + HX(g)