qualitative analysis practice quiz

When 6 M NaOH is added and the mixture is heated, which observation confirms NH₄⁺?

a) Brown solid forms
b) Gas with vinegar-like smell
c) Gas with pungent odor; red litmus turns blue
d) Blue solution appears

C

The correct equation for this test is:
a) NH₄⁺ + OH⁻ → NH₄OH (s)
b) NH₄⁺ + H₂O → NH₃ + H₃O⁺
c) NH₄⁺ + OH⁻ ⇌ NH₃ (g) + H₂O (l)
d) NH₄⁺ + Cl⁻ → NH₄Cl (s)

C

Adding Zn metal to a blue Cu²⁺ solution causes:
a) Blue fades; Zn surface darkens
b) White precipitate forms
c) Brown solid forms
d) Solution turns clear

A

The balanced redox equation is:
a) Cu²⁺ + Zn → Cu + Zn²⁺
b) Zn²⁺ + Cu → Cu²⁺ + Zn
c) Cu + 2 Zn → Cu²⁺ + Zn²⁺
d) Cu + Zn²⁺ → Cu²⁺ + Zn

A

After adding 6 M HNO₃ to the tube containing Cu metal, you observe:
a) White precipitate forms
b) Solution becomes brown
c) Blue solution forms with gas bubbles
d) No visible change

C

Which equation represents that reaction?
a) Cu + 2 H⁺ → Cu²⁺ + H₂ (g)
b) 3 Cu + 8 H⁺ + 2 NO₃⁻ → 3 Cu²⁺ + 2 NO + 4 H₂O
c) Cu + 4 NO₃⁻ → Cu(NO₃)₄²⁻
d) Cu²⁺ + 2 NO₃⁻ → Cu(NO₃)₂

B

Adding 6 M NH₃ to the Cu²⁺ solution gives a color change to:
a) Pale blue
b) Royal blue
c) Colorless
d) Brown

B

The complex formed is:
a) [Cu(H₂O)₆]²⁺
b) [CuCl₄]²⁻
c) [Cu(NH₃)₄]²⁺
d) Cu(OH)₂ (s)

C

Adding 0.2 M K₄[Fe(CN)₆] produces:
a) Deep blue solution
b) Yellow-brown precipitate
c) Cloudy white suspension
d) No visible change

B

The correct equation is:
a) Cu²⁺ + 4 NH₃ → [Cu(NH₃)₄]²⁺
b) 2 Cu²⁺ + [Fe(CN)₆]⁴⁻ → Cu₂[Fe(CN)₆] (s)
c) Cu²⁺ + [Fe(CN)₆]⁴⁻ → Cu[Fe(CN)₆]₂
d) Cu + NO₃⁻ → Cu²⁺ + NO₂

B

Reagent used to identify Ca²⁺:
a) 1 M Na₂HPO₄
b) 6 M NH₃
c) 1 M K₂C₂O₄
d) 6 M HNO₃

C

Observation confirming Ca²⁺ presence:
a) Blue solution
b) Brown solid
c) White precipitate
d) No change

C

Balanced equation:
a) Ca²⁺ + C₂O₄²⁻ → CaC₂O₄ (s)
b) Ca²⁺ + 2 OH⁻ → Ca(OH)₂ (s)
c) Ca²⁺ + Fe(CN)₆⁴⁻ → Ca₂[Fe(CN)₆]
d) Ca + O₂ → CaO₂

A

Reagents used for Mg²⁺ test:
a) 6 M NH₃ + 1 M Na₂HPO₄
b) 6 M NaOH + 1 M K₂C₂O₄
c) 6 M HNO₃ + NH₄Cl
d) 6 M NH₃ + K₄[Fe(CN)₆]

A

Observation confirming Mg²⁺:
a) Blue solution
b) Brown precipitate
c) Cloudy white solid
d) Gas bubbles

C

Correct equation:
a) Mg²⁺ + NH₃ + HPO₄²⁻ → MgNH₄PO₄ (s)
b) Mg²⁺ + C₂O₄²⁻ → MgC₂O₄ (s)
c) Mg²⁺ + 2 OH⁻ → Mg(OH)₂ (s)
d) Mg²⁺ + NO₃⁻ → Mg(NO₃)₂

A

Red litmus turning blue indicates:
a) Acidic solution (pH < 7)
b) Basic solution (pH > 7)
c) Neutral solution
d) Unsaturated solution

B

The Zn metal darkens during the Cu²⁺ test because:
a) It dissolves completely
b) Cu metal deposits on it
c) It reacts with NH₃
d) It forms ZnO

B

Which ion is responsible for blue or royal-blue color changes?
a) NH₄⁺
b) Ca²⁺
c) Mg²⁺
d) Cu²⁺

D

Which two ions form white precipitates in their confirmatory tests?
a) Cu²⁺ and NH₄⁺
b) Ca²⁺ and Mg²⁺
c) NH₄⁺ and Mg²⁺
d) Cu²⁺ and Ca²⁺

B

The main purpose of comparing reference and unknown solutions is:
a) To standardize acid concentration
b) To calculate molality
c) To identify ions by matching reaction patterns
d) To check solution density

C

Which reagent is used to test for NH₄⁺ ions?
a) 6 M HNO₃
b) 6 M NH₃
c) 6 M NaOH
d) 1 M K₂C₂O₄

C

What observation confirms NH₄⁺?
a) Brown gas released
b) Pungent gas + red litmus → blue
c) White precipitate
d) Colorless solution

B

Which safety precaution is most relevant when heating the NH₄⁺ sample?
a) Keep tube covered to trap gas
b) Waft the gas — do not inhale directly
c) Shake vigorously for better reaction
d) Test blue litmus first

B

What is the purpose of adding Zn metal?
a) To form Cu(OH)₂
b) To oxidize Cu²⁺ to Cu³⁺
c) To reduce Cu²⁺ to Cu metal
d) To remove H₂ gas

C

Observation when Zn is added to Cu²⁺ solution:
a) Blue fades; Zn darkens
b) Brown solid forms
c) White ppt forms
d) No visible change

A

After HNO₃ is added:
a) Blue solution + gas bubbles
b) Red solution + odor
c) White ppt
d) No change

A

Reaction for Cu + HNO₃:
a) Cu + 2 H⁺ → Cu²⁺ + H₂
b) 3 Cu + 8 H⁺ + 2 NO₃⁻ → 3 Cu²⁺ + 2 NO + 4 H₂O
c) Cu²⁺ + 2 NO₃⁻ → Cu(NO₃)₂
d) Cu + NO₂ → Cu(NO₂)₂

B

After adding NH₃, what happens?
a) White ppt
b) Royal-blue complex forms
c) Brown gas
d) Colorless solution

B

Formula of the royal-blue complex:
a) Cu(OH)₂
b) Cu(NO₃)₂
c) [Cu(NH₃)₄]²⁺
d) [CuCl₄]²⁻

C

Adding K₄[Fe(CN)₆] to Cu²⁺ solution produces:
a) Yellow-brown ppt (Cu₂[Fe(CN)₆])
b) Blue gas
c) Cloudy white liquid
d) Brown gas

A

Correct equation:
a) 2 Cu²⁺ + [Fe(CN)₆]⁴⁻ → Cu₂[Fe(CN)₆] (s)
b) Cu²⁺ + NH₃ → Cu(NH₃)₄²⁺
c) Cu + NO₃⁻ → Cu(NO₃)₂
d) Cu²⁺ + 2 Cl⁻ → CuCl₂ (s)

A

Reagent that identifies Ca²⁺ ions:
a) 6 M NH₃
b) 1 M K₂C₂O₄
c) 6 M NaOH
d) 1 M Na₂HPO₄

B

Observation confirming Ca²⁺:
a) White ppt (CaC₂O₄)
b) Blue solution
c) Brown solid
d) Colorless solution

A

Equation for Ca²⁺ test:
a) Ca²⁺ + C₂O₄²⁻ → CaC₂O₄ (s)
b) Ca²⁺ + 2 OH⁻ → Ca(OH)₂ (s)
c) Ca²⁺ + NH₃ → CaNH₃²⁺
d) Ca + O₂ → CaO₂

A

Reagents for Mg²⁺ test:
a) 6 M HNO₃ + K₄[Fe(CN)₆]
b) 6 M NH₃ + 1 M Na₂HPO₄
c) 1 M K₂C₂O₄ + 6 M HCl
d) 6 M NH₃ + 1 M KOH

Observation confirming Mg²⁺:
a) Blue solution
b) Brown ppt
c) Cloudy white solid
d) Gas evolution

C

Equation for Mg²⁺ reaction:
a) Mg²⁺ + 2 OH⁻ → Mg(OH)₂ (s)
b) Mg²⁺ + NH₃ + HPO₄²⁻ → MgNH₄PO₄ (s)
c) Mg²⁺ + C₂O₄²⁻ → MgC₂O₄ (s)
d) Mg²⁺ + Cl⁻ → MgCl₂ (s)

B

Red litmus → blue indicates pH is:
a) < 7 (acidic)
b) > 7 (basic)
c) = 7 (neutral)
d) variable

B

What does a double horizontal line ( = ) mean in the flow chart?
a) Precipitate
b) Separation step
c) Soluble ions present in solution
d) Confirmed ion

C

Why is centrifuging used?
a) To speed up reactions
b) To separate precipitate from solution
c) To dissolve solid
d) To mix reagents

B

The blue/royal-blue color is always due to:
a) Cu²⁺ complexes
b) Ca²⁺ ions
c) NH₄⁺ gas
d) Zn²⁺ ions

A

The solution becomes paler when Zn reacts with Cu²⁺ because:
a) Cu²⁺ is reduced to Cu metal
b) Zn is oxidized to ZnO
c) NH₃ is released
d) H⁺ is neutralized

A

A blue clear liquid at the start most likely contains:
a) NH₄⁺
b) Ca²⁺
c) Mg²⁺
d) Cu²⁺

D

If no color change occurs after adding Na₂HPO₄ and NH₃, what does that mean?
a) Mg²⁺ present
b) Mg²⁺ absent
c) Ca²⁺ present
d) Cu²⁺ present

B

During the experiment, which cation produces a gas?
a) Cu²⁺
b) NH₄⁺
c) Ca²⁺
d) Mg²⁺

B

Why compare unknown and reference solutions?
a) To identify ions by matching observations
b) To find molality
c) To measure pH
d) To standardize acid

A

Waste from acidic tests (HNO₃, K₄[Fe(CN)₆]) should go into:
a) Basic aqueous waste container
b) Acidic aqueous waste container
c) Solid waste bin
d) Organic waste

B

Reacted Zn metal pieces should be disposed in:
a) Solid waste bucket
b) Acidic aqueous waste
c) Basic aqueous waste
d) Sink drain

A

Which step involves gas evolution besides NH₄⁺ testing?
a) Cu + HNO₃ reaction (NO gas formed)
b) Mg²⁺ test
c) Ca²⁺ test
d) Cu + NH₃ reaction

A

Which of the following shows an acidic condition?
a) Blue litmus → red
b) Red litmus → blue
c) No change in litmus
d) Formation of white ppt

A

In the NH₄⁺ test, the wet red litmus paper turns blue because:
a) NH₄⁺ neutralizes acid
b) NH₃ gas is basic
c) Cu²⁺ is oxidized
d) Zn is reduced

B

What type of reaction is Cu²⁺ + Zn → Cu + Zn²⁺?
a) Single-displacement (redox)
b) Double-replacement
c) Acid-base
d) Decomposition

A

Formation of Cu₂[Fe(CN)₆] is a/an ____ reaction.
a) Redox
b) Neutralization
c) Precipitation
d) Gas formation

C

Which ion is confirmed by formation of MgNH₄PO₄ (s)?
a) NH₄⁺
b) Cu²⁺
c) Ca²⁺
d) Mg²⁺

D

Which ion is identified by formation of CaC₂O₄ (s)?
a) Ca²⁺
b) Cu²⁺
c) Mg²⁺
d) NH₄⁺

A

Which observation indicates Cu²⁺ after adding NH₃?
a) Colorless solution
b) Deep royal-blue solution
c) Brown ppt
d) Gas evolution

D

NH₄⁺ test: Which equation corresponds to the formation of a basic gas that turns red litmus blue?
a) NH₄⁺ + OH⁻ ⇌ NH₃ (g) + H₂O (l)
b) NH₄⁺ + H₂O ⇌ NH₃ + H₃O⁺
c) Cu²⁺ + 4 NH₃ → [Cu(NH₃)₄]²⁺
d) Ca²⁺ + C₂O₄²⁻ → CaC₂O₄ (s)

A

Cu²⁺ test: Which equation represents copper’s reduction by zinc?
a) 3 Cu + 8 H⁺ + 2 NO₃⁻ → 3 Cu²⁺ + 2 NO + 4 H₂O
b) Cu²⁺ + Zn → Cu (s) + Zn²⁺ (aq)
c) Cu²⁺ + 4 NH₃ → [Cu(NH₃)₄]²⁺
d) 2 Cu²⁺ + [Fe(CN)₆]⁴⁻ → Cu₂[Fe(CN)₆] (s)

B

The reaction forming a royal-blue solution corresponds to which ion?
a) NH₄⁺
b) Cu²⁺
c) Ca²⁺
d) Mg²⁺

B

The reaction forming a yellow-brown precipitate corresponds to which ion?
a) Cu²⁺
b) Mg²⁺
c) Ca²⁺
d) NH₄⁺

A

Which ion is confirmed by the reaction:
Ca2+ + C2O42− → CaC2O4(s)
a) Cu²⁺
b) Mg²⁺
c) Ca²⁺
d) NH₄⁺

C

Which reaction forms a white crystalline solid of magnesium ammonium phosphate?
a) Mg²⁺ + C₂O₄²⁻ → MgC₂O₄ (s)
b) Mg²⁺ + NH₃ + HPO₄²⁻ → MgNH₄PO₄ (s)
c) Cu²⁺ + 4 NH₃ → [Cu(NH₃)₄]²⁺
d) Zn + Cu²⁺ → Cu + Zn²⁺

B

A pungent gas with red litmus turning blue confirms:
a) Cu²⁺
b) NH₄⁺
c) Ca²⁺
d) Mg²⁺

B

A deep royal-blue solution confirms the formation of which complex?
a) [Cu(H₂O)₆]²⁺
b) [Cu(NH₃)₄]²⁺
c) [CuCl₄]²⁻
d) [Cu(OH)₄]²⁻

B

A yellow-brown precipitate after adding K₄[Fe(CN)₆] indicates:
a) Cu₂[Fe(CN)₆] formed → Cu²⁺ present
b) Zn²⁺ ions present
c) CaC₂O₄ formed → Ca²⁺ present
d) MgNH₄PO₄ formed → Mg²⁺ present

A

A white precipitate that forms with K₂C₂O₄ and dissolves in acid belongs to which ion?
a) Cu²⁺
b) Mg²⁺
c) NH₄⁺
d) Ca²⁺

D

A cloudy white solid formed after adding NH₃ and Na₂HPO₄ indicates:
a) Cu²⁺
b) Ca²⁺
c) Mg²⁺
d) NH₄⁺

C

A solution turning pale blue, then royal blue through two steps corresponds to:
a) Cu²⁺ reduced to Cu⁺
b) Cu²⁺ reactions with Zn then NH₃
c) Mg²⁺ and Na₂HPO₄
d) NH₄⁺ and NaOH

B

Which pair correctly matches the color change with the reaction?
a) Blue → royal-blue : Cu²⁺ + NH₃ → [Cu(NH₃)₄]²⁺
b) Colorless → brown : NH₄⁺ + OH⁻ → NH₃ + H₂O
c) Colorless → white ppt : Cu²⁺ + Zn → Cu + Zn²⁺
d) Pale blue → yellow : Ca²⁺ + C₂O₄²⁻ → CaC₂O₄

A

Which reaction is both acidic and gas-evolving?
a) NH₄⁺ + OH⁻ → NH₃ + H₂O
b) 3 Cu + 8 H⁺ + 2 NO₃⁻ → 3 Cu²⁺ + 2 NO + 4 H₂O
c) Cu²⁺ + 4 NH₃ → [Cu(NH₃)₄]²⁺
d) Ca²⁺ + C₂O₄²⁻ → CaC₂O₄

B

A reduction–oxidation (redox) reaction in this experiment is:
a) Cu²⁺ + 4 NH₃ → [Cu(NH₃)₄]²⁺
b) Cu²⁺ + Zn → Cu + Zn²⁺
c) Ca²⁺ + C₂O₄²⁻ → CaC₂O₄
d) Mg²⁺ + HPO₄²⁻ → MgNH₄PO₄

B

A precipitation reaction in this experiment is:
a) Cu²⁺ + Zn → Cu + Zn²⁺
b) 3 Cu + 8 H⁺ + 2 NO₃⁻ → 3 Cu²⁺ + 2 NO + 4 H₂O
c) 2 Cu²⁺ + [Fe(CN)₆]⁴⁻ → Cu₂[Fe(CN)₆] (s)
d) NH₄⁺ + OH⁻ → NH₃ + H₂O

C