The Properties Of Nitric Acid Essay Research

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Contents Page

No.??????????????? . .Introduction?????????????????????????????????????????????????????????????????????????????????????????????????? 1. Plan ??????????????????????????????????????????????????????????????????????????????????????????????????????????? 3 ? ????????? Outline of method ??????????? Reactions. Results:????????????????????????????????????????????????????????? ??????????????????????????????????????????????? 7 ??????????? ?Acidic properties ??????????? ?Oxidizing properties ??????????? ?Reducing properties.. Discussion:??????????????????????????????????????????????????????????????????????????????????????????????????? 9 ??????????? Evaluation. Bibliography????????????????????????????????????????????????????????????????????????????????????????????????? 14. Chemical equipment?s and lists.??????????????????????????????????????????????????????????????????? 15Introduction: An investigation on the properties of Nitrous acid.??????????? The study

under this investigation was concerned with the acid base and redox reactions

of Nitrous acid. Nitrous acid is a weak acid of ka 4.7 x 10-4

formed from the reaction:NaNo2(aq)? + HCl(aq) ®

HNO2(aq)? +NaCl(aq). ?????????????????

??????????????????????(nitrous

acid) ??????????? Related

studies have shown that a pale blue solution is formed from this reactions a

result of an unstable oxide N2O3 and that HNO2

is an unstable compound because it decomposes very fast at room temperature. It

was hence used up immediately after being made from its constituent?s

reactants, Sodium nitrite and Hydrochloric acid. The instability of the compound means that it

disproportionates at standard room temperature .HNO2(aq)? —– HNO3(aq)?

+NO (g) ????????????

??????(nitric acid)?????? (nitrogen monoxide)??????????? Disproportionation

occurs when one of the reactant molecule in a reaction forms two products, one

product which is obtained by the oxidation of the reactant molecule and the

other by reduction. To limit this effect, Le Chatelier?s principle applied that

cooling the system will shift the equilibrium to the exothermic direction of

the equation to minimise the temperature decrease. In this case an ice bath was

used to drive the reaction towards the left-hand side. This inevitably limits

the dispropornation reactions.To demonstrate the acidic properties of Nitrous

acid, the three standard tests were set.Acid?

+? base/alkali??? ®??? Salt + waterAcid?

+? Metal??? ®????? Metal Salt?? + HydrogenAcid? +

Carbonate???? ®???? Salt?

+? Carbondioxide? +?

WaterThe redox reactions involve reductions and

oxidations. To question the view that HNO2 behaved as either a

reductant, oxidant or both, scientific theories and experiments were applied

based on the fact that it displays the characteristics set by the following

standards As a reducing

agent it reduces another specie by donating electrons to it. As an oxidising

agent it oxidises another specie by removing electrons from it. To practically demonstrate the acid base, redox

reactions of HNO2 the following reagents were used based on factors

concerned with cost, availability and the nature of their reactions.1Reagents: Acidic reactions Magnesium solid Sodium hydroxide solution Sodium Carbonate solidReduction reactions Bromine water Pottasuim manganate (VII) solution Sodium dichromate (VI) solutionOxidation reactions Pottasium iodide solution Iron (II) sulphate solution Sulphur dioxide solutionIn all the cases, the anticlockwise rule

was applied to make predictions on whether a reaction took place and possible

outcomes of the products. Appropriate tests were carried out in some of the

reactions to distinguish formation of products if any from that of a mixture of

the reactants. Prior to making an aqueous solution of HNO2,

consideration were given to the small scale laboratory procedure and the

following safety precautions: ·

Use standard laboratory concentrations of 2M. ·

Wear laboratory coats and goggles. ·

Avoid inhaling toxic nitrogen monoxide gas (use

fume cupboard)2 Plan :

Preparation of Nitrous acid ?An aqueous

solution of 2M HNO2 was made from cold acidified aqueous solution of

sodium nitrite from the equation.NaNo2(aq)? + HCl(aq)??

®? HNO2(aq)? +?

NaCl(aq)Calculations:Moles of NaNo2 and HCL, ratio 1:1 Amount needed = 100cm3 of 2M HNO2 Amount of HCl = 50cm3 of 2M HCl????? ????? 50 x 2??? = 0.1 moles ??????????? 1000Moles of NaNo2 = 0.1 moles Mass = 0.1?

x? (RMM? 69g) ??????????? ??????????? =6.9g??????????? 6.9g

of NaNo2 makes up 50cm3 of 2M solution.Outline

of method:·

Set up a conical flask placed into an ice bath. ·

Weigh 6.9g of solid NaNo2 and dissolve

in 50cm3 of distilled water. ·

Pour solution into conical flask

inside ice bath. ·

Cool down to a temperature range of (0 ? 5)0C in ice bath. ·

Add 50cm3 of 2M HCl to conical flask ·

Place apparatus in fume cupboard ·

Carry out tests with the conical flask placed in

ice bath.Procedure: 3cm3 of Nitrous acid was

used to react in all cases to 3cm3 and small portions of reactant

solutions and solids . A table of results was set up to summarise observations

of colour changes, fumes and result of tests.3 Reactions: Acid ? base??????????? Magnesium ??????????????????????????????? ?A metal plus an acid will result in the

formation of a metal salt and hydrogen gas as shown in the equation.2HNO2(aq)?? +??? Mg(s)?? ®?Mg(NO2)2

(aq)? +?

H2 (g) ??????????????????????????? ??????? ??????(magnesium nitrite)Prediction:? An exothermic reaction will occur as there

will be effervescence of hydrogen. Magnesium solid dissolves.??????????? Sodium hydroxide ??????????????????????? This

acid ?base reaction should produce salt and water as a result of

neutralization.HNO2(aq)?

+? NaOH(aq)? ®? NaNo2 (aq)? +?? H2O

(l) ?????????????? ???????????????????? (sodium

nitrite)Prediction : A

neutralization reaction should occur producing a salt. A neutral pH should

indicate a green colour using a universal indicator.??????????? Sodium Carbonate ??????????????????????? A

reaction involving carbonates produces a metal salt, water and carbondioxide

gas.HNO2(aq) + NaCO3(s)? ®

NaNo2(aq) +CO2(g) + H2O(l) ??????????????????????????????????? ??? (sodium nitrite)Prediction: The

chemical equation suggests effervescence of the carbondioxide gas and a neutral

pH for the metal salt formation of a green colour using the universal

indicator. Solution should turn cloudy with limewater (CaOH2)

producing white precipitates of CaCO3(s) ??????????? CO2(g)

+ CaOH2 (aq) ®

CaCO3(s) + H2O(l) ????????????????

?????????????????????????????? (calcium

carbonate)4 Oxidation Pottasuim Iodide ??????????????????????? The

anticlockwise rule applies that I -(aq) will be oxidised to I2(s)

according to the equation: ??????????????????????????????????????????????? ????????????????????????????????????????????????????

E I2(s)?

+2e —-? 2I-(aq)???????????????????????????????????????????????????????????????? +

0.54V 2HNO2(aq) + 2H+(aq) + 2e

—–?? 2NO(g) + H2O(l)????? ?????? ??+0.99VFull equation 2HNO2(aq) + 2H+(aq) +2I-(aq)? ®

I2(s) + 2NO(g) + 2H2O(l)Prediction:

Iodine will be formed and its presence detected by a blueblack colour from a

starch indicator. Brown fumes given off, due to NO2 gas formation

from ?2NO(g) + O2(g)? ®

2NO2(g) ????? ????? ????(air)?????? (brown

fumes)Iron (II) sulphate ??????????????????????????????? ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ?? E Fe3+(aq)? + e —- Fe2+(aq)?????????????????????????????????????????????????????? +0.76V HNO2(aq) + H+(aq) + e —-

NO(g) + H2O (l)?????????????????????? ??????????? +0.99VFull equation HNO2(aq) + H+ (aq) + Fe2+(aq)

® Fe3+(aq)

+ NO(g) + H2O(l)Prediction:? Fe3+ will be produced as brown

precipitates of Fe(OH)3(s) ,when the solution mixture is reacted with

sodium hydroxide. Fe3+(aq) + OH-(aq) ® Fe(OH)3(s) ?????????? ???????????????????????? (brown ppt)??????????? Sulphur dioxide ??????????????????????????????????????????????????????????????????????????????????????????????? E SO42-(aq) + 4H+(aq)

+2e —-? SO2(aq) +2H2O(l)?????? ?????????

+0.17V 2HNO2(aq) + 2H+(aq) +2e

—– 2NO(g) +2H2O(l)?? ????????? +0.99V ? Full equation 2HNO2(aq) + SO2(aq) +2H+

(aq) + 2H2O(l) ®

SO42-(aq) + 4H+(aq) + 2NO(g) + 2H2O(l)Prediction:

SO42-(aq) will be produced as white precipitates of BaSO4(s),

when the solution mixture is reacted with Barium Chloride. ??????????????????????? Ba2+(aq) + SO42-(aq)

® BaSO4(s) ??????????????????????????????????????????????????????????? ?(white ppt)5 Reduction??????????????? ?Bromine water ???????????????????????????????? ??????????????????????????????????????????????????????????????????????????????????????????????? E NO3-(aq) + 3H+(aq)

+2e —-?? HNO2(aq) + H2O(l)???????????? +0.94V Br2(l)?

+? 2e —–? 2Br-(aq)?????????????????????????????????????????? ??????? +1.07VFull equation HNO2(aq) +Br2(l) + H2O(l)

® NO3-(aq)

+ 3H+(aq)? +2Br-(aq)Prediction: Bromine

water should be reduced to bromide ions and the positive test of creamy

precipitates of silver bromide should be observed after adding a portion of

AgNO3(aq) to the solution. Br-(aq) +? Ag+(aq) ®

AgBr(s) ????????? ????????????????????????? (creamy ppt).??????????? Pottasuim manganate(VII) ??????????????????????????????????????????????????????????????????????????????????????????????? ? E 5NO3-(aq) +15H+(aq)

+10e —– 5HNO2(aq) + 5H2O(l)???????? +0.94V 2MnO42-(aq) + 16H+ (aq)

+10e — 2Mn2+(aq) + 8H2O(l)???????? +1.52VFull equation 5HNO2(aq)

+ 2MnO42-(aq) + 16H+(aq) +10e —5NO3-(aq)

+2Mn2+(aq) +15H+(aq) +8H2O(l).Prediction:

Purple Mn7+(aq) according to the equation will be reduced to

colourless Mn2+(aq) ??????????? Sodium

dichromate(VI) ??????????????????????????????????????????????????????????????????????????????????? ???????????? E NO3-(aq)

+ 3H+(aq) + e —- HNO2(aq) + H2O(l)?? ?????????????? +0.94V Cr2O72-(aq)

+ 14H+(aq) + e — 2Cr3+(aq) + 7H2O(l)?? ?????????? ????????????+1.33VFull

equation HNO2(aq)

+Cr2O7 2- (aq) +14H+(aq) + H2O(l)® 2Cr3+(aq)

+NO3-(aq) +3H+(aq) + 7H2O(l)Prediction:

The anticlockwise rule applies that Nitrous acid in this case will reduce

orange Cr6+(aq) to green Cr3+(aq). 6Results

demonstrating properties of Nitrous Acid. Acidic

properties ?Reagents Predictions Observations Magnesium Solid Exothermic reaction should occur as

hydrogen gas is given off. Magnesium solid dissolves. Vigorous reaction. Effervescence of H2 (g)

leaves test tube warm. Brown gas produced. Sodium hydroxide solution A neutralization reaction in this case should

result to a neutral pH. Colour should turn green with a universal indicator. Colourless

+indicator(purple)+ HNO2(green) Sodium carbonate solid The metal salt NaNo2 will be formed

with a neutral ph. Carbon dioxide and water produced. CO2 presence

detected using limewater to produce white CaCO3(s) Colourless+ indicator(blue) + HNO2 (green) Effervescence of CO2(g) With limewater white ppt produced. Carbonate dissolves. Conclusions : The reactions occurred as anticipated

producing conclusive sets of results. With the magnesium, a’ pop’ test was

carried out to confirm H2 gas produced. Brown fumes given off by the

system was unexplained in the predictions, but a qualitative reason was looked

on further in the discussion. A change in pH during the NaOH(aq) test clearly

indicated the formation of a salt, which had a neutral pH. The Carbonate

reaction and test demonstrated that the metal salt NaNo2 was formed

and carbon dioxide evolved.Oxidising properties ?Reagents Predictions Observations Pottasuim Iodide I2 will be formed and the presence

demonstrated by a blueblack colour with starch. Probable brown fumes of NO oxidation. ?Fizzing. Colourless

+HNO2(black ppt) +

starch (bluishblack) brown

fumes IronIISulphate Fe3+(aq) produces as brown ppt of

Fe(OH)3(s) when the mixture is reacted with NaOH(aq) Probable brown fumes of NO oxidation. Brown fumes Clear solution +HNO2 (darkgreen ppt) + NaOH(brown ppt) Sulphur dioxide Mixture of acid and SO2 reacts to

give White precipitates of BaSO4(s) with

a??? mixture of BaCl2 Mixture +BaCl2® white ppt. Conclusions: HNO2

has the tendency to act as an oxidant and oxidised the above reactants,

approved by the observation and standard tests carried out. A detailed

explanation of the mechanisms observed was given in the discussion.Reducing properties ?Reagents Predictions Observations ?Bromine

water Br2(l) reduces to Br-(aq) Br-(aq) + Ag+(aq)® AgBr(s) creamy ppt Brown

+HNO2(clear) +

AgNo3(aq) creamy ppt. ?Pottasuim maganate(VII) Purple Mn7+ reduces to colourless Mn2+ Colour change Purple +HNO2(colourless) Sodium dichromate (VI) ?Anticlockwise rule applies that Orange Cr6+(aq)

reduces to greenCr3+ Orange+HNO2(green) Conclusion: Conclusive evidence from the above tests suggests

that HNO2(aq) has the tendency to behave as a reducing specie.8 Discussion??????????????? Using

the anticlockwise rule had clearly with in effect suggested the mechanism in

which the reactions occurred. A much negative E value increases the tendency

for HNO2 to act as a reducing agent, and a more positive E value

allows the tendency to act as an oxidising agent. The reason to which why these

chemical reactions occur will be discussed in relation to Gibbs energy. The

following data summarises the findings of the HNO2 reactions. As an Acid ,?

the results were obtained as predicted. Effervescence produced

by the reaction with magnesium, warmed the test tube as it was an exothermic

reaction. Brown fumes were however produced from this reaction without being

predicted. The exothermic nature of this reaction could account for the

oxidation of NO(g). A high confidence level in results was confirmed with the

?pop? test for hydrogen gas and with limewater in the carbonate reaction to

check for CO2(g). Significantly the carbonate reaction had outlined

HNO2 to be a stronger acid compared to carbonic acid as it had

protonated the carbonate ion to release carbondioxide. As an Oxidising agent, the E chart

illustrates as to why the observations of the reactions fit into the prediction

pattern. In this case HNO2 has more tendency to accept elactrons so

has a more positive E than that of the reactants.Pottasuim iodide,

ironIIsulphate and sulphur dioxide were oxidised by HNO2 which

itself was reduced by release of NO2 fumes.When pottasuim iodide was

used, the initial black precipitates seen was a result of iodine formation

which was confirmed with starch to give the typical blueblack colour. HNO2(aq) + H+(aq) + 2I-(aq)

® I2(s)

+ NO(g) + H2O(l) ??????????????????????????????????? (bluishblack???? ?

(oxidised to brown fumes of NO2 ) ?with starch)Nitrous acid reduced to nitrogen monoxide Iodide oxidised to Iodine. (oxidation no.increase

+1) The

reaction with ironIIsulphate produced a lime green coloured solution. After the

addition of NaoH, the brown ppt. Produced was a positive test for the presence

of Fe3+(aq). HNO2(aq) +H+(aq) + Fe2+(aq)® Fe3+(aq)

+ NO(g) +H2O(l) ??????????????????????????????????? (green)??

(brown with NaOH)Nitrous acid reduced to nitrogen monoxide Fe2+ oxidised to Fe3+(oxidation

no. increase +1) The

Sulphur dioxide reaction shows the formation of white ppt. of sulphate ions

after the addition of barium chloride solution. 2HNO2(aq) +2H+(aq) + SO2(aq)+2H2O(l)® SO42-(aq)

+4H+(aq) +2NO(g) +2H2O(l) ??????????????????????????????????????????????????????????? ?( white ppt with BaSO4 )Nitrous acid reduced to Nitrogen monoxide S4+ oxidised to S6+(oxidation

no. increase +2)??????????? In

all the equations the oxidation number of nitrogen inHNO2 ( +3) had

been reduced to (+2) in NO and so therefore HNO2? is an oxidising agent. 9 As a Reducing agent the E charts

illustrates that from the anticlockwise rule that Nitrous acid is oxidised to

nitrate and the corresponding reactants reduced as it has a more negative E

value and more tendency to donate electrons. The brown bromine water was reduced to colourless

Br- in solution. Br- reacted with Ag+ to form

AgBr(s). HNO2(aq) + Br2(l) + H2O(l)

® NO3-(aq)

+ 2Br-(aq) + 3H+(aq). ??????????????????????????????????????????????????????????????????????? (creamy

ppt with AgNO3) HNO2 oxidised? to NO3- Br2 reduced to Br-

(oxidation no. decrease ?1)When

KMnO4(aq) was reacted. A colour change from purple to

colourless? was shown the colour change

showed that Mn2+ was formed. 5HNO2(aq) + 2MnO42-(aq)

+16H+(aq)®

5NO3-(aq) + 15H+(aq) +2Mn2+(aq) +

4H2O(l) ??????????????????????? (purple)??????????????????????????????????????????????????????????? (colourless)HNO2 oxidised to NO3- Mn7+ reduced to Mn2+ (oxidation

no. decrease ?5)The Na2Cr2O7

reaction showed that Cr3+ was formed, the colour change from

orange to green was observed. HNO2(aq)

+Cr2O72-(aq) +14H+(aq) +H2O(l)® 2Cr3+(aq)

+NO3-(aq) +3H+(aq)+7H2O(l) ??????????? ?????? (orange)??????????????????????????????????????? (green)HNO2

oxidised to NO3- Cr6+

reduced to Cr3+ (oxidation no.decrease ?3)??????????? In all the above equations, Nitrous

acid was oxidised to nitrate ion. The

oxidation number of nitrogen in HNO2 (+3) increased to (+5) in NO3-. HNO2? is a reducing agent.??????????? Related studies as to why the redox

reactions of Nitrous acid occur could be viewed by the entropy changes in the

reactions. The study by the American scientist Willard Gibbs reviews that the

relationship between the total entropy of a chemical reaction and the electromotive

force of the corresponding cell is??????????????????????? ∆S total

= -zFEcell ??????????????????????????????????? ?????????? T As

chemists are only concerned with the reaction inside the test tube excluding

the surroundings the Gibbs free energy?

∆G was used and expressed as??????????????????????? ?∆G = -T∆S total10For a

change, in a reaction to have taken place of its own accord, For a spontaneous

change ?∆S

must be positive. It therefore follows that for a spontaneous

change? ∆Gmust be negative. A

reaction is usually described as going to completion if kc =1010 or

greater ; this corresponds to a value of ∆G of

about ? 60kJmol-1 or a greater negative value.? ∆G = ∆G

products? – ∆G

reactantsIn the

Reduction reaction Bromine

water HNO2(aq)

+Br2(l) +H2O(l) ®

NO3-(aq) +3H+(aq) +2Br-(aq) (-37.2)?????????

0.0?? (-237.2)???? ?

(111.3)?????????? 0.0?????? ?

(-104.0)?∆G = [ 2(-104.0) ? (113.0)] ?

[(-237.2)-(37.2)] ? ? = -44.9 kJmol-1?∆S total =-44.9 x 1000? = +150Jmol-1k-1? , thus the reaction is feasible. ??????????? ????

-298Pottasuim

maganate(VII) 5HNO2(aq)

+ 2MnO42-(aq) + 16H+(aq) + 5H2O(l)® 5NO3-(aq)

+ 2Mn2+(aq) +15H+(aq)+8H2O(l) (-37.2)???????????? (-447.2)?????????????????????? ? 0.0???? ?

(-237.2)???????? (-111.3)??????? (-228.0)? ????? 0.0???????

(-237.2)? ∆G? = [5(-111.3) +2(-228.0) +8(-237.2)] ? [5(-37.2) + 2(-447.2) +

8(-237.2)]?? = -643.6 kJmol-1?? ∆S total = -643.6 x 1000

= +2159 Jmol-1k-1 , thus the reaction is feasible. ??????????????????????? -298Sodium

dichromate(VI) HNO2(aq)

+ Cr2O72- (aq) +14H+(aq) +H2O(l)

®2Cr3+(aq)

+NO3-(aq) +3H+(aq) +7H2O(l) (-37.2)????

(-1301.2)??? ????? 0.0????? (-237.2)???? ?? (-204.9)?????? (-111.3)?????? 0.0??????????? ????????? (-237.2)? ∆G = [7(-237.2) ? 111.3 +

2(-204.9)] ? [-37.2 ? 1301.2 ? 237.2]?= -605.5 kJmol-1? ∆S total = -605.5 x 1000

= +2031.9 Jmol-1k-1 , thus the reaction is feasible. ??????????????????????? -29811 In the

Oxidation reactionPottasuim

iodide HNO2(aq)

+ 2H+(aq) + 2I-(aq)®I2(s)

+ 2NO(g) +2H2O(l) (-37.2)??????????? 0.0?????? (-51.6)????? 0.0?????? (86.6)?????? (-237.2)?∆G = [2(-237.2) =2(86.6)] ?

[2(-51.6) + 2(-37.2)]?= -123.6 kJmol-1?∆S total = -123.6 x 1000

= +414.7 Jmol-1K-1, thus the reaction is feasible. ??????????????????????? -298Iron (II)sulphate HNO2(aq) + Fe2+(aq) + H+(aq)

® Fe3+(aq)

+NO(g) +H2O(l) (-37.2)???????????? (-78.9)???? 0.0?????????????? (-4.6)?? ???

(86.6)???? (-237.2)?∆G =

[86.6 ? 4.6 ? 237.2] ? [-78.9 ? 37.2]= -39.1 kJmol-1? ∆S total

= -39.1 x 1000 = +131.2 Jmol-1k-1 , thus the

reaction is feasible. ??????????????????????? -298?The

Sulphur dioxide data was unavailable.The pH of 2M Nitrous acidKa = [H+(aq)]eq[NO2-(aq)]eq???????????? Ka value = 4.7 x10-4 ??????????? ??? [HNO2(aq)]eqSince very little HNO2? dissociates [HNO2(aq)]aq = [HNO2(aq)]initialKc = ?????????????????

[ H+(aq)]eq x [H+(aq)]?? ??????????? ???????? ??{HNO2(aq)]eq??????? 4.7

x10-4 = [H+(aq)]2 ??????????????????????? ??? 2.0 ?????????? Ц9.4 x10-4

= [H+(aq)], ??????????? 3.0

x 10-2 = [H+(aq)]. pH = -log10[3.0 x 10-2] ??? = 1.5 12 Nitrous acid is a weak acid and will only ionize

little in water. The Kc value is therefore small due to incomplete ionization.

The? ∆G, E and ∆S total

values have demonstrated that the reactions were feasible.EVALUATION: ?The

technique and procedures applied to the test was of good measures, as most of

the predictions were observed. To raise the confidence levels in the results if

this investigation was to be repeated a larger range of reactants would be

used. As with the acidic properties, a buffer solution of Nitrous acid and

sodium nitrite could be set up to observe the buffering effect of the acid, and

its reactions with oxides to look for a pattern. In the redox reactions,

vanadium compounds could be used as the variable oxidation numbers of vanadium

are easily distinguished in simple reactions by the colours produced by its

ions.13 Bibliography ??????????? ??????????? Relevant

references were obtained from the following sources.Nuffield Advanced Science Chemistry student book (third edition)????????????????????????????????????????????????????????????????????????? (longman

publishers)Chemistry in context (third edition)????????????????????????? P.W.

Atkins ??????????????????????????????????????????????? M.J.

Glugston ??????????????????????????????????????????????? M.J.

Fazer ??????????????????????????????????????????????? RAY

Jones. ??????????????????????????????????????????????????????????????????????? Advanced Chemistry (first edition) ??????????????????????????????????????????????? Michael

Clugston ??????????????????????????????????????????????? Rosalind

Flemming. ??????????????????????????????????????????????????????????????????????????????????????????????? (Oxford

Publishers)14Chemical

Equipment?s and lists. Equipments?? ??????????????????????????????????????????????????????????????????????? Conical Flask Spatula Ice bath Thermometer

Mass balance PipetteSolutions and Materials Distilled water Iron(II)sulphate Pottasuim iodide Pottasuim manganate Sodium dichromate Magnesium Solid Hydrochloric acid Sodium nitrite Sodium hydroxide Sodium carbonate Sulphur dioxide Bromine water? ?????????????????????????????????????????????????????????? ? Indicators ?Universal

indicator Starch Silver nitrite Barium Chloride. 15