chapter(2) - Chemical analysis

Question 1

All chlorides are (1) —— in water except (2)——–

Answer 1

(1)soluble - (2)(lead(Pb), silver(Ag) ,mercury(Hg))

Question 2

All bromides are (1) —— in water except (2)——–

Answer 2

(1)soluble - (2)(lead(Pb), silver(Ag) ,mercury(Hg))

Question 3

All iodides are (1) —— in water except (2)——–

Answer 3

(1)soluble - (2)(lead(Pb), silver(Ag) ,mercury(Hg))

Question 4

All sulphides of metals are (1)——— in water except——-

Answer 4

1)insoluble (2)(barium, calcium, magnesium, sodium, potassium, ammonium)

Question 5

all carbonates are ——— in water except ——–

Answer 5

1)insoluble 2)(sodium(Na) , potassium(K) , ammonium(NH4))

Question 6

all silver salts are —— in water except ——

Answer 6

1)insoluble 2)(silver nitrate , silver acetate(CH3COOAg))

Question 7

All nitrates are ——- in water

Answer 7

soluble

Question 8

all acetates are ——- in water

Answer 8

soluble

Question 9

all sodium salts are —– in water

Answer 9

soluble

Question 10

all potassium salts are —– in water

Answer 10

soluble

Question 11

all ammonium salts are —– in water

Answer 11

soluble

Question 12

Q: What is the confirmatory test for carbonates and bicarbonates?

Answer 12

A: The confirmatory test uses magnesium sulfate (MgSO₄)

Question 13

Q: How does magnesium sulfate (MgSO₄) differentiate between carbonates (CO₃²⁻) and bicarbonates (HCO₃⁻)?

Answer 13

Carbonates react with MgSO₄ to form magnesium carbonate (MgCO₃), which appears as a white precipitate:
MgSO₄+Na₂CO₃→MgCO₃(whiteppt)+Na₂SO₄

Bicarbonates initially react with MgSO₄ to form soluble magnesium bicarbonate (Mg(HCO₃)₂), which needs to be heated to produce MgCO₃ as a white precipitate:
MgSO₄+2NaHCO₃→Mg(HCO₃)₂(soluble)+Na₂SO₄
Mg(HCO₃)₂→MgCO₃(whiteppt)+H₂O+CO₂(onheating)

Question 14

q.All bicarbonate salts are ______ in water.

Answer 14

A: Soluble.

Question 15

All carbonate salts of metals are ______ in acids.

Answer 15

Soluble.

Question 16

All carbonate salts of metals are ______ in water, except sodium carbonate, potassium carbonate, and ammonium carbonate.

Answer 16

A: Insoluble.

Question 17

Q: Which carbonate salts are soluble in water?

Answer 17

A: Sodium carbonate (Na₂CO₃), potassium carbonate (K₂CO₃), and ammonium carbonate ((NH₄)₂CO₃).

Question 18

Q: A reaction evolves a gas with a very irritating smell, which turns a paper acidified with potassium dichromate green. Identify the compound responsible for the green color.

Answer 18

A: Chromium(III) sulfate [Cr₂(SO₄)₃].

Question 19

Q: What happens when sodium sulfite (Na₂SO₃) reacts with dilute hydrochloric acid (HCl)?

Answer 19

Sodium sulfite reacts with dilute HCl to form sodium chloride (NaCl), water (H₂O), and sulfur dioxide (SO₂) gas:
Na₂SO₃+2HCl→2NaCl+H₂O+SO₂

The SO₂ gas reacts with acidified potassium dichromate, turning it green due to the formation of chromium(III) sulfate.

Question 20

Q: A reaction evolves a gas with a rotten egg smell. When this gas contacts a paper wetted with lead(II) acetate, it forms a black precipitate. Identify the gas and the black precipitate.

Answer 20

A:

Gas: Hydrogen sulfide (H₂S).
Black precipitate: Lead(II) sulfide (PbS)

Question 21

Q: What happens when a solid sulfide reacts with dilute hydrochloric acid (HCl)?

Answer 21

A:

The reaction produces hydrogen sulfide gas (H₂S):

The H₂S gas reacts with paper wetted with lead(II) acetate to form black precipitate lead(II) sulfide (PbS):
H₂S+(CH₃COO)₂Pb→2CH₃COOH+PbS(blackppt)

Question 22

Q: A reaction produces a gas with a strong rotten egg smell. This gas reacts with a paper soaked in a specific solution, forming a black precipitate. Identify the solution used on the paper, the gas, and the precipitate formed.

Answer 22

Solution on the paper: Lead(II) acetate [(CH₃COO)₂Pb].
Gas: Hydrogen sulfide (H₂S).
Black precipitate: Lead(II) sulfide (PbS).

Question 23

Q: What happens when sodium thiosulfate (Na₂S₂O₃) reacts with dilute hydrochloric acid (HCl)?

Answer 23

A: The reaction produces sulfur dioxide gas (SO₂) and solid sulfur (S) suspended in the solution:
Na₂S₂O₃+2HCl→2NaCl+SO₂+S(solid)+H₂O

Question 24

Q: A reaction between a sodium compound and a dilute acid generates a gas with a pungent odor, along with a solid that appears as a yellow precipitate in the solution. Identify the sodium compound and the gas produced in this reaction.

Answer 24

Sodium compound: Sodium thiosulfate (Na₂S₂O₃).
Gas: Sulfur dioxide (SO₂).

Question 25

Q: How can you differentiate between sulfite and sulfide salt solutions?

Answer 25

A: Use silver nitrate (AgNO₃):

Question 26

Q: What happens when a sulfide salt solution reacts with silver nitrate (AgNO₃)?

Answer 26

A: The reaction produces a black precipitate of silver sulfide (Ag₂S): Na₂S + 2AgNO₃ → 2NaNO₃ + Ag₂S (black ppt)

Question 27

Q: A test involves adding a specific nitrate solution to two different salt solutions. One salt produces a white precipitate that turns black upon heating, while the other yields a black precipitate. Identify the two types of salts and the nitrate solution used.

Answer 27

A: Salts: Sodium sulfite (Na₂SO₃) produces the white precipitate, and sodium sulfide (Na₂S) produces the black precipitate. Nitrate solution: Silver nitrate (AgNO₃).

Question 28

Q: In a chemical test, a colorless solution reacts with another solution, leading to the formation of a black solid upon addition of the first solution. The black solid remains unchanged upon heating. Identify the initial solution and the nature of the black solid formed.

Answer 28

A: Initial solution: Silver nitrate (AgNO₃). Black solid: Silver sulfide (Ag₂S).

Question 29

Q: What happens when iodine is added to sodium thiosulfate (Na₂S₂O₃)?

Answer 29

A: The brown color of the iodine solution disappears due to the formation of colorless sodium iodide (NaI): Na₂S₂O₃ + I₂ → 2NaI + Na₂S₄O₆

Question 30

Q: When a specific solution is added to a thiosulfate salt, a color change occurs, indicating that a colorless compound has formed. Identify the solution added and the resulting compound.

Answer 30

A: Solution added: Iodine (I₂). Resulting compound: Sodium iodide (NaI).

Question 31

Q: A reaction occurs where a sodium compound is added to an acidified solution of a potassium salt, resulting in the disappearance of a violet color. Identify the sodium compound, the potassium salt, and describe the changes that occur during the reaction.

Answer 31

Sodium compound: Sodium thiosulfate (Na₂S₂O₃). Potassium salt: Potassium dichromate (K₂Cr₂O₇) acidified with sulfuric acid (H₂SO₄). Changes: The violet color of potassium permanganate disappears as it is reduced to colorless manganese ions (Mn²⁺), and sodium thiosulfate undergoes reduction to form soluble colorless salts.