Chemistry - HCl

Question 1

Mg (s) + dil. HCl (aq) →?

Answer 1

Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g)
Observation: Effervescence (bubbles) of hydrogen gas (H₂)

Question 2

Zn (s) + dil. HCl (aq) →?

Answer 2

Zn (s) + 2HCl (aq) → ZnCl₂ (aq) + H₂ (g)
Observation: Effervescence (bubbles) of hydrogen gas (H₂)

Question 3

Fe (s) + dil. HCl (aq) →?

Answer 3

• Fe (s) + 2HCl (aq) → FeCl₂ (aq) + H₂ (g)
• Observation: Effervescence (bubbles) of hydrogen gas (H₂)
• Note: FeCl₂ is iron(II) chloride.

Question 4

CuO (s) + dil. HCl (aq) →?

Answer 4

CuO (s) + 2HCl (aq) → CuCl₂ (aq) + H₂O (l)
Note: CuCl₂ is copper(II) chloride (blue in solution).

Question 5

NH₄OH (aq) + dil. HCl (aq) →?

Answer 5

NH₄OH (aq) + HCl (aq) → NH₄Cl (aq) + H₂O (l)

Question 6

Na₂CO₃ (s) + dil. HCl (aq) →?

Answer 6

• Na₂CO₃ (s) + 2HCl (aq) → 2NaCl (aq) + H₂O (l) + CO₂ (g)
• Observation: Effervescence of carbon dioxide gas (CO₂)

Question 7

CuCO₃ (s) + dil. HCl (aq) →?

Answer 7

CuCO₃ (s) + 2HCl (aq) → CuCl₂ (aq) + H₂O (l) + CO₂ (g)
Observation: Effervescence of CO₂, solution turns blue (CuCl₂ forms).

Question 8

NaHCO₃ (s) + dil. HCl (aq) →?

Answer 8

NaHCO₃ (s) + HCl (aq) → NaCl (aq) + H₂O (l) + CO₂ (g)
Observation: Effervescence of CO₂.

Question 9

Ca(HCO₃)₂ (s) + dil. HCl (aq) →?

Answer 9

Ca(HCO₃)₂ (s) + 2HCl (aq) → CaCl₂ (aq) + 2H₂O (l) + 2CO₂ (g) \n* Observation: Effervescence of CO₂.

Question 10

Na₂SO₃ (s) + dil. HCl (aq) →?

Answer 10

Na₂SO₃ (s) + 2HCl (aq) → 2NaCl (aq) + H₂O (l) + SO₂ (g) \n* Observation: Effervescence of sulfur dioxide gas (SO₂).

Question 11

MgSO₃ (s) + dil. HCl (aq) →?

Answer 11

MgSO₃ (s) + 2HCl (aq) → MgCl₂ (aq) + H₂O (l) + SO₂ (g) Observation: Effervescence of SO₂.

Question 12

NaHSO₃ (s) + dil. HCl (aq) →?

Answer 12

NaHSO₃ (s) + HCl (aq) → NaCl (aq) + H₂O (l) + SO₂ (g) \n* Observation: Effervescence of SO₂.

Question 13

Na₂S (s) + dil. HCl (aq) →?

Answer 13

Na₂S (s) + 2HCl (aq) → 2NaCl (aq) + H₂S (g) \n* Observation: Effervescence of hydrogen sulfide gas (H₂S) (smells like rotten eggs).

Question 14

FeS (s) + dil. HCl (aq) →?

Answer 14

FeS (s) + 2HCl (aq) → FeCl₂ (aq) + H₂S (g)
Observation: Effervescence of H₂S.

Question 15

CuS (s) + dil. HCl (aq) →?

Answer 15

CuS (s) + 2HCl (aq) → CuCl₂ (aq) + H₂S (g) \n* Observation: Effervescence of H₂S, black CuS changes to blue CuCl₂.

Question 16

AgNO₃ (aq) + dil. HCl (aq) →?

Answer 16

AgNO₃ (aq) + HCl (aq) → AgCl (s) + HNO₃ (aq) \n* Observation: White precipitate of silver chloride (AgCl) forms.

Question 17

Pb(NO₃)₂ (aq) + dil. HCl (aq) →?

Answer 17

Pb(NO₃)₂ (aq) + 2HCl (aq) → PbCl₂ (s) + 2HNO₃ (aq) \n* Observation: White precipitate of lead(II) chloride (PbCl₂) forms. \n* Note: PbCl₂ is soluble in hot water.

Question 18

Na₂S₂O₃ (aq) + dil. HCl (aq) →?

Answer 18

Na₂S₂O₃ (aq) + 2HCl (aq) → 2NaCl (aq) + SO₂ (g) + S (s) + H₂O (l) \n* Observation: Effervescence of SO₂, yellow precipitate of sulfur (S) forms.

Question 19

MnO₂ (s) + 4HCl (conc.) →?

Answer 19

MnO₂ (s) + 4HCl (conc.) → MnCl₂ (aq) + 2H₂O (l) + Cl₂ (g) \n* Observations: A gas (chlorine) is evolved which is greenish-yellow in color and has a strong, choking smell. Reaction requires heat (Δ).

Question 20

PbO₂ (s) + 4HCl (conc.) →?

Answer 20

PbO₂ (s) + 4HCl (conc.) → PbCl₂ (aq) + 2H₂O (l) + Cl₂ (g) \n* Observations: Chlorine gas evolved. Reaction requires heat (Δ).

Question 21

Pb₃O₄ (s) + 8HCl (conc.) →?

Answer 21

Pb₃O₄ (s) + 8HCl (conc.) → 3PbCl₂ (aq) + 4H₂O (l) + Cl₂ (g) \n* Observations: Chlorine gas evolved. Reaction requires heat (Δ).

Question 22

2KMnO₄ (s) + 16HCl (conc.) →?

Answer 22

2KMnO₄ (s) + 16HCl (conc.) → 2KCl (aq) + 2MnCl₂ (aq) + 8H₂O (l) + 5Cl₂ (g) \n* Observations: Chlorine gas evolved (more abundantly than with the other oxides). Reaction requires heat (Δ). The intense purple color of permanganate fades.

Question 23

K₂Cr₂O₇ (s) + 14HCl (conc.) →?

Answer 23

K₂Cr₂O₇ (s) + 14HCl (conc.) → 2KCl (aq) + 2CrCl₃ (aq) + 7H₂O (l) + 3Cl₂ (g) \n* Observations: Chlorine gas evolved. Reaction requires heat (Δ). The orange dichromate solution turns green as CrCl₃ forms.

Question 24

What happens when a glass rod dipped in ammonia solution is brought near HCl vapors?

Answer 24

• Dense white fumes of ammonium chloride (NH₄Cl) are formed.
• NH₃ (aq) + HCl (vapour) → NH₄Cl (dense white fumes)

Question 25

What happens when silver nitrate solution is added to dilute HCl (acidified with dilute HNO₃)?

Answer 25

* A curdy white precipitate of silver chloride (AgCl) is obtained. \n* AgNO₃ (aq) + HCl (aq) → AgCl (white ppt.) + HNO₃ (aq) \n* The AgCl precipitate is soluble in excess ammonia solution and insoluble in dilute HNO₃ and cold water. \n* AgCl + 2NH₄OH (excess) → [Ag(NH₃)₂]Cl (soluble diamine silver chloride) + 2H₂O \n* Note: This test also distinguishes dilute HCl from dilute HNO₃.

Question 26

What happens when a mixture of manganese dioxide and concentrated HCl is heated?

Answer 26

A greenish-yellow gas (chlorine, Cl₂) is evolved. MnO₂ + 4HCl (conc.) → MnCl₂ + 2H₂O + Cl₂ (g) Note: This reaction proves that HCl contains chlorine.

Question 27

What are some major industrial uses of hydrochloric acid?

Answer 27

In the manufacture of: Dyes: , Drugs , Textiles Artificial silk

Question 28

What are some other uses of hydrochloric acid?

Answer 28

* For cleaning metals (e.g., removing rust). * In the leather industry. * In the electroplating industry.