inorganic chemistry laboratory experimental report

Experiment 1: Observation of the color of alkaline earth metal flame Produce: - Dip a clean filter paper into a saturated

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY Office of International Study Program

Faculty of Chemical Engineering

INORGANIC CHEMISTRY LABORATORY

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CONTENT

UNIT 2: Alkaline Earth Metals (Group IIA) 3

UNIT 6: Hydrogen - Oxygen - Sulfur (𝐻2 – 𝑂2 – 𝑆) 10

UNIT 8: Copper-Silver- Gold (𝐶𝑢 – – 𝐴𝑔 𝐴𝑢) (GROUP IB) 18

UNIT 10: Group VIB (CHROMIUN) 28

UNIT 12: transition metal Iron-Cobalt-Nickel (𝐹𝑒 − 𝐶𝑜 − 𝑁𝑖) (GROUP VIIIB) 33

- Water hardness and method for softening water

II Experimental Results:

1 Experiment 1: Observation of the color of alkaline earth metal flame

Produce:

- Dip a clean filter paper into a saturated 𝐶𝑎𝐶𝑙2

- Hold it over the flame

- Observe the color of the flame

- Repeat with saturated solutions of 𝑆𝑟𝐶𝑙2and 𝐵𝑎𝐶𝑙2

Phenomenon of flame’s color:

2 Experiment 2: Reaction of an alkaline earth metal with H O 2

Prepare 2 test tubes adding

Observe the state of

mixture and reaction at

room temperature and

of solution turns to light pink and s small

amount of gas appears

- At high temperature, the reaction occurs quicker, the pink color becomes darker and spread throughout the solution, more gas

appeared

- When 𝑁𝐻4𝐶𝑙 is added, the color of solution fades until it turns to colorless, at the same

- Creation of 𝐻2 gas that escaped air bubbles and 𝑀𝑔(𝑂𝐻)2 that covered the

surface of Mg slows down the reaction

𝑀𝑔 + 2𝐻2𝑂 → 𝑀𝑔(𝑂𝐻)2+ 𝐻2

- Mg(OH)2 dissolve partly in water, producing OH- that turning phenolphthalein into pink at the interface between Mg and water

𝑀𝑔( )𝑂𝐻2⇌𝑀𝑔2++ 2𝑂𝐻−

- At high temperature, 𝑀𝑔(𝑂𝐻)2 is more soluble in water, making the solution color darker At the same time, the coverage of 𝑀𝑔( )𝑂𝐻2 decreases making the first reaction occur stronger, creating more air bubbles

- When 𝑁𝐻4𝐶𝑙 is added, it dissolves 𝑀𝑔(𝑂𝐻)2, which released the surface of

Mg, making the reaction between Mg and

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time, more gas releases After that, the solution turns to pink again

𝐻2𝑂 occurred more stronger and increased the a mount of 𝐻2 air bubbles 𝑀𝑔(𝑂𝐻)2+ 𝑁𝐻4𝐶𝑙 ⇄ 𝑀𝑔𝐶𝑙2+ 𝑁𝐻3+ 𝐻2𝑂

- At the same time, 𝑀𝑔(𝑂𝐻)2 is dissolved, the equilibrium of reaction is shifted to the backwards direction, which making

𝑂𝐻− decrease therefore phenolphthalein turned back to being colorless

- Pink color reappears due to 𝑁𝐻3 is produced in the reaction and 𝑂𝐻− from the dissolution of 𝑀𝑔( )𝑂𝐻2

Conclusion: Alkaline-earth metals react weakly with water at room temperature, but react

strongly when heated or in the presence of suitable catalyst

3 Experiment 3: Alkaline earth metal hydroxide synthesis

3.1) synthesis and properties of 𝑴𝒈(𝑶𝑯)𝟐

Synthesis 𝑀𝑔(𝑂𝐻)2 from

sodium hydroxide and

magnesium salt, then

centrifuge to get the solid

Decant the liquid and

- No phenomenon occurred

𝑀𝑔( )𝑂𝐻2+ 2𝐻𝐶𝑙 → 𝑀𝑔𝐶𝑙2+ 2𝐻2𝑂

- 𝑁𝑎𝑂𝐻 and 𝑀𝑔(𝑂𝐻)2 both have the basic properties

𝑀𝑔( )𝑂𝐻2+ 𝑁𝐻4𝐶𝑙

→ 𝑀𝑔𝐶𝑙2+ 2𝑁𝐻3+ 2𝐻2𝑂

3.2) Synthesis and properties of alkaline earth metal hydroxides:

Produce:

- Prepare 4 separate test tubes containing 1 mL of 𝐵𝑎2+, 𝑆𝑟2+, 𝐶𝑎2+, 𝑀𝑔2+ 0.5M solutions

- Add 0.5 mL of 1M 𝑁𝑎𝑂𝐻 solution to each of test tubes

- Observe the formation of precipitate and compare the precipitate quantity

Phenomenon:

- White precipitate created in all test tubes

- The amount of precipitate increase in order of 𝐵𝑎2+, 𝑆𝑟2+, 𝐶𝑎2+ and 𝑀𝑔2+

Reactions and Explanation:

𝑀𝑔2++ 2𝑂𝐻−⇄𝑀𝑔( )𝑂𝐻2

𝑆𝑟2++ 2𝑂𝐻−⇄ ( )𝑆𝑟𝑂𝐻2

𝐶𝑎2++ 2𝑂𝐻−⇄ ( )𝐶𝑎𝑂𝐻2

𝐵𝑎2++ 2𝑂𝐻−⇄𝐵𝑎 𝑂𝐻( )2From 𝑀𝑔 𝐵𝑎 to , the atomic radius increases leading to the decrease in the attractive force of nucleus on its valence electrons Moreover, due to oxygen has a high electronegativity which pulls electrons to itself, making the hydroxyl group highly polar making it easy to be dissolved

in water

Conclusion: Hydroxide of alkaline earth metals can be synthesized by the reaction between

their soluble salt with strong basic hydroxide solution From 𝑀𝑔 𝐵𝑎 to , the solubility of these hydroxide decreases

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salts

1) Slowly add 0.5 mL of 2N

sulfuric acid to 4 separate

test tubes Then centrifuge

the solutions to observe the

- The precipitate are insoluble

𝐶𝑎2++ 𝑆𝑂42−⇄ 𝐶𝑎𝑆𝑂4

𝐵𝑎2++ 𝑆𝑂42−⇄ 𝐵𝑎𝑆𝑂4

𝑆𝑟2++𝑆𝑂42−⇄ 𝑆𝑟𝑆𝑂4

- From 𝑀𝑔 𝐵𝑎 to , the radius of ion

𝑋2+ increases, so the polarizability

of it in water and hydrate energy decreases Moreover, the activation

of the cations is larger than lattice energy From these reasons above, the solubility decreases from 𝑀𝑔 to

𝐵𝑎

- When adding excess 𝐻2𝑆𝑂4, the concentration of 𝑆𝑂42− increases, making the equilibrium shifts to the forward direction reaction, increasing the amount of precipitate

Conclusion: The solubility of alkaline earth metals decrease from 𝑀𝑔 𝐵𝑎 to

5 Experiment 5: Evaluation of water hardness

Produce:

- Extract 10ml hard water by using pipet 10ml into 250ml erlenmeyer flask

- Add distilled water in order to obtain around 100ml of volume in total

- Add 5ml buffer solution pH=10, add 4 to 7 drops of ERIO-T indicator color

- Shake and titrate using 0.02N EDTA solution until the indicator color changes from red to light blue

Conclusion: The total remaining content of 𝑀𝑔2+ and 𝐶𝑎2+is 14.6 (mN)

6 Experiment 6: Water softening

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𝑀𝑔(𝑂𝐻)2+ 𝑁𝐻4𝐶𝑙 ⇄ 𝑀𝑔𝐶𝑙2+ 𝑁𝐻3+ 𝐻2𝑂 Other 𝑁𝐻4 salts also applicable because 𝐶𝑙− don’t have role in the reaction above This reaction

is basically between 𝑁𝐻4+ and 𝑂𝐻−

𝑜

→ 𝑀𝑔𝐶𝑂3+ 𝐶𝑂2+ 𝐻2𝑂 Using 𝐶𝑎( )𝑂𝐻2

𝐶𝑎(𝐻𝐶𝑂3)2+ 𝐶𝑎( )𝑂𝐻2→ 2𝐶𝑎𝐶𝑂3+ 2𝐻2𝑂 𝑀𝑔(𝐻𝐶𝑂3)2+ 𝐶𝑎(𝑂𝐻)2→ 𝐶𝑎𝐶𝑂3+ 𝑀𝑔𝐶𝑂3+ 2𝐻2𝑂

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UNIT 6: HYDROGEN - OXYGEN - SULFUR

(𝑯𝟐 – 𝑶 – 𝑺)𝟐

- Preparation of hydrogen and oxygen gas: by water displacement method

- Chemical properties of hydrogen, oxygen, sulfur:

o Hydrogen: atomic hydrogen is a stronger reducing agent than molecular hydrogen

o Oxygen: oxygen is a strong oxidizing agent, easily oxidizing metals and non-metals

to form oxides Oxygen also maintains combustion

o Sulfur: at high temperature, sulfur has strong oxidizing properties

Experiment Description of interesting

experiments and observations

Explain the phenomenon, writing equation, analysis

and conclusion

1 Synthesis

of

Hydrogen

- Install the air gathering system

Introduce five pellets of zinc

metal to the test tube prior to

adding 5 𝑚𝐿 of concentrated 𝐻𝐶𝑙

Collect the gas produced with a

small test tube filled with water

upside down in a pot

Igniting the hydrogen gas

released at the top of the pipe has

𝑍𝑛 + 2𝐻𝐶𝑙 → 𝐶𝑙𝑍𝑛 2+ 𝐻2↑

Because hydrogen reacts with oxygen mixed in the test tube and in the gas system, there is an explosion Initially, the amount of oxygen was more, so there was a loud explosion

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Result:

mMorh’s salt weighed = 12.83g

mMorh’s salt theory = 5

2 Experiment 2: Properties of 𝑭𝒆𝟐+ and 𝑭𝒆𝟑+ compounds

+ Tube 2: 𝐻2𝑂2 solution which

was previously acidized using

𝐻2𝑆𝑂4

Blue precipitate appears

𝐹𝑒2++ 𝐾3[𝐹𝑒(𝑆𝐶𝑁)6] → ]𝐹𝑒3[𝐹𝑒(𝑆𝐶𝑁)6]2(Turnbull blue) + 2𝐾+

2𝐹𝑒2++ 3𝐻2𝑂2 + 2𝐻+

→ 2𝐹𝑒3+ + 4𝐻2𝑂 + 𝑂2

The solution’s color changes to yellow

Black precipitate appears

Appearance of green precipitate, turning brown in air

6𝐹𝑒2+ + 𝐶𝑟2𝑂7− + 14𝐻+ → 6𝐹𝑒3+ + 2𝐶𝑟3+ (moss-green) +7𝐻2𝑂

5𝐹𝑒2+ + 𝑀𝑛𝑂4− + 8𝐻+

→ 5𝐹𝑒3++ 𝑀𝑛2++ (𝑦𝑒𝑙𝑙𝑜𝑤) + 4𝐻2𝑂

𝐹𝑒2+ + 𝑆 → 𝐹𝑒𝑆2−

𝐹𝑒2+ + 2𝑂𝐻− → 𝐹𝑒(𝑂𝐻)2 4𝐹𝑒(𝑂𝐻)2 + 𝑂 + 2 𝐻2 2𝑂 → 4𝐹𝑒(𝑂𝐻)3

2𝐹𝑒3+ + 𝐼 →− 𝐹𝑒2+ + 𝐼2 (charcoal purple)

- When KI is excess:

𝐼2 + → 𝐾𝐼𝐾𝐼 3 (brown soil)

Conclusion:

- 𝐹𝑒2+ is susceptible to be oxidized

- 𝐹𝑒3+ salt is stable in the air and has oxidation property in acids

3 Experiment 3: Properties of 𝑪𝒐𝟐+and 𝑵𝒊𝟐+ compounds

- Add 5 drops 𝐶𝑜𝐶𝑙2 and add

few drops 2N 𝑁𝑎𝑂𝐻 to 2 test

tubes

- The solution’s color is pink

- Blue precipitate appears and changes to the red color afterwards

- Pink is the color of complex 𝐶𝑜(𝐻2𝑂)62+

- Before: 𝐶𝑜𝐶𝑙2 + 𝑁𝑎𝑂𝐻 → 𝐶𝑜𝑂𝐻𝐶𝑙(blue)

- After: 𝐶𝑜𝑂𝐻𝐶𝑙 + 𝑁𝑎𝑂𝐻 → 𝐶𝑜(𝑂𝐻)2 (𝑟𝑒𝑑) + 𝑁𝑎𝐶𝑙

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- Put in 2 test tubes each 5

The color stays unchanged

Air bubbles appear

Precipitate turns gray

Precipitation turns gray and air bubbles appear

4𝐶𝑜(𝑂𝐻)2 + 𝑂2 + 2𝐻2𝑂 → 4𝐶𝑜(𝑂𝐻)3(grey)

2𝐶𝑜(𝑂𝐻)2 + 𝐻2𝑂2→ 2𝐶𝑜(𝑂𝐻)3(grey) 2𝐻2𝑂2→ 2𝐻2𝑂 + 𝑂2

+ Part 1: The precipitate dissolves and creates a yellow solution

+ Part 2: The precipitate doesn't dissolve

- Reddish-pink precipitate appears

+ Part 1: The precipitate dissolved slightly to create a light pink solution + Part 2: No phenomenon

𝐹𝑒3+ + 3𝑂𝐻− → 𝐹𝑒(𝑂𝐻)3 brown)

(reddish-𝐹𝑒(𝑂𝐻)3+ 3𝐻+→ 𝐹𝑒3+ + 3𝐻2𝑂

𝐶𝑜2+ + 2𝑂𝐻−→ (𝑂𝐻)𝐶𝑜 2(reddish-pink)

𝐶𝑜(𝑂𝐻)2 + 2𝐻 +

→ 𝐶𝑜2+ (𝑙𝑖𝑔ℎ𝑡 𝑝𝑖𝑛𝑘) + 2𝐻2𝑂

- Green precipitate appears

+ Part 1: The precipitate dissolved to create a pale pink solution

+ Part 2: No phenomenon

𝑁𝑖2+ + 2𝑂𝐻− → 𝑁𝑖(𝑂𝐻)2 ( green)

𝑁𝑖(𝑂𝐻)2+ 𝐻 → + 𝑁𝑖2+ + 2𝐻2𝑂

Before adding HCl and NaOH:

After adding HCl and NaOH:

- In alkali, hydroxides are more stable and insoluble

4 Experiment 4: Properties of 𝑪𝒐𝟐+and 𝑵𝒊𝟐+compounds

The color change of 𝑪𝒐𝟐+

compound:

- Write letters on filter paper

and view the letter color

Dry filter paper by flame

The Tsugaep reaction of

Nickel:

- The letters’s color is pink

Drying by the flames of alcohol lamps The pink color disappears and the blue purple –color appears instead

- In the heating process, complex 𝐶𝑜(𝐻2𝑂)62+ loses water to form a smaller complex 𝐶𝑜(𝐻2𝑂)42+ having a blue –purple color

𝑁𝑖2+ + 2𝑂𝐻− → 𝑁𝑖(𝑂𝐻)2(green)

- Blood red precipitate appears

𝑁𝑖(𝑂𝐻)2 + 6𝑁𝑁𝐻3 → [𝑁𝑖 𝑁𝐻( 3)6](𝑂𝐻)2 (dark blue)

2𝐶𝐶4𝐻8𝑁2𝑂2 + 𝑁𝑖(𝑂𝐻)2

→ 𝑁𝑖(𝐶4𝐻7𝑁2𝑂2)2+ 2𝐻2𝑂

- The 𝑁𝑖(𝐶4𝐻7𝑁2𝑂2)2 complex has a square shape with weak acidity and basicity in the water or in the diluted

NH4OH solution, but it dissolves well in strong acid and base

Conclusion:

- The complex has a square shape with weak acidity and basicity in the water or in the diluted

𝑁𝐻4𝑂𝐻 solution, but it dissolves well in strong acid and base Therefore, when replacing

𝑁𝐻4𝑂𝐻 with 𝑁𝑎𝑂𝐻, the enough amount will lead to an appearane of the light red precipitate

On the contrary, adding excess 𝑁𝑎𝑂𝐻 could make the precipitate dissolve immediately

- The Tsugaep reaction is used to calculate and quantify 𝑁𝑖2+ in the solution

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5 Experiment 5: Properties of 𝑪𝒐𝟐+ and 𝑵𝒊𝟐+ compou nds

The solution turns blue

Blue precipitate appears and create a dark blue solution

𝐶𝑜2++ 2𝑂𝐻−→ (𝑂𝐻)𝐶𝑜 2 (pink) 𝐶𝑜(𝑂𝐻)2+ 6 𝑁𝐻3 →

[𝐶𝑜(𝑁𝐻3)6](𝑂𝐻) (brown) 2The blue color appears because the concentrated 𝑁𝐻4𝑂𝐻 absorbs water from on the complex 𝐶𝑜(𝐻2𝑂)62+

𝐶𝑜(𝐻2𝑂)62+(𝑝𝑖𝑛𝑘) + 4𝐶𝑙−→ 𝐶𝑜𝐶𝑙4− (𝑏𝑙𝑢𝑒) 6𝐻+ 2𝑂

𝑁𝑖2+ + 2𝑂𝐻−→ 𝑁𝑖(𝑂𝐻)2 ( green) 𝑁𝑖(𝑂𝐻)2+ 6𝑁𝐻3 → [𝑁𝑖 𝑁𝐻( 3)6](𝑂𝐻) 2(dark -blue)

- 𝑁𝑖(𝑂𝐻)2 and 𝐶𝑜(𝑂𝐻)2 are soluble in 𝑁𝐻3 due to their ablility to form stable complexes

- Both 𝐶𝑜2+ and 𝑁𝑖2+ are able to form complexes with 𝐶𝑙− and those complexes may change

the color of solution

2 How is double salt different from complex salt?

A mixture of many salts that

crystallize at the same time

A compound

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force between salt molecules between the central ions and the ligands Exist in solid form and dissolve

into constituent species in solution

Exist In both solid and liquid states and still maintain their identity

Completely dissociate into its ions in

3 What ions are present in the Morh’s salt solution?

The Morh’s salt solution is 𝐹𝑒𝑆𝑂4(𝑁𝐻4)2𝑆𝑂4 6𝐻2𝑂

- After dissolving the Morh’s salt in water, two 𝑁𝐻4+, two 𝑆𝑂42−and one 𝐹𝑒2+ will be produced To prove that:

- Add concentrated 𝑁𝑎𝑂𝐻 solution and heat gently

𝐹𝑒2+ + 2𝑂𝐻− → 𝐹𝑒(𝑂𝐻)2

4𝐹𝑒(𝑂𝐻)2+ 𝑂 + 2𝐻2 2𝑂 → 4𝐹𝑒(𝑂𝐻)3

- There is a mossy green precipitate that rapidly turns brown in the air The presence of 𝐹𝑒2+

- There is a presence of urine gas The presence of 𝑁𝐻4+

𝑁𝐻4+ +𝑂𝐻− →𝑁𝐻3+ 𝐻2𝑂

- Add 𝐵𝑎𝐶𝑙2 salt solution

𝐵𝑎2+ + 𝑆𝑂42−→ 𝐵𝑎𝑆𝑂4

- A white precipitate is formed that is insoluble in strong acids The presence of 𝑆𝑂42−

4 Explain the procedure for the synthesis of Morh’s salt solution

Dissolve Fe in dilute 𝐻2𝑆𝑂4 to form 𝐹𝑒2+ The heating speeds up the dissolution reaction and it also makes 𝐻2𝑆𝑂4 become denser, which will oxidize 𝐹𝑒2+ to 𝐹𝑒3+

as a reducing agent that will keep 𝐹𝑒2+: from being oxidized to 𝐹𝑒3+ in the double salt Soak the becher in cold water for a more favorable crystallization process

5 What reactions are used to detect the presence of 𝑭𝒆𝟐+ and 𝑭𝒆𝟑+?

For the detection of 𝐹𝑒2+: 𝐹𝑒2+ reacts with potassium ferricyanide will form the turnbull blue precipitate of ferrous ferricyanide

3𝐹𝑒2+ + 2[𝐹𝑒(𝐶𝑁)6]3− → 𝐹𝑒 𝐹𝑒3[ ( )𝐶𝑁6]2

For detection of Fe : Fe reacts with potassium ferrocyanide to form potassium berlin blue 3+ 3+precipitate of ferric ferrocyanide

4𝐹𝑒3++ 3[𝐹𝑒(𝐶𝑁)6]4−→ 𝐹𝑒4[𝐹𝑒( )𝐶𝑁 ]6 3

6 What kind of reaction as conducted in the experiment 4b? What is it used for?

The Tsugaep reaction is a complexation reaction of 𝑁𝑖( )𝐼𝐼: nickel dimethylglyoximatein dilute 𝑁𝐻3 solution, used for qualitative and quantitative determination of Ni in solution 2+