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1009 available questions

Chemistry · Question 711

Which alkali metal listed is least metallic?

  1. Lithium
  2. Sodium
  3. Rubidium
  4. Caesium
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Correct answer: A

Lithium

Metallic character increases down Group 1, so lithium is least metallic.

Chemistry · Question 712

What oxidation state do alkali metals show in their compounds?

  1. +1
  2. +2
  3. −1
  4. −2
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Correct answer: A

+1

Alkali metals lose their single valence electron to form +1 ions.

Chemistry · Question 713

Which listed alkali metal is the most reactive?

  1. Lithium
  2. Sodium
  3. Rubidium
  4. Caesium
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Correct answer: D

Caesium

Group 1 reactivity increases down the group, making caesium the most reactive listed.

Chemistry · Question 714

Potassium reacts with excess oxygen mainly to form:

  1. K₂O
  2. K₂O₂
  3. K₂O₃
  4. KO₂
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Correct answer: D

KO₂

Potassium forms potassium superoxide, KO₂, in excess oxygen.

Chemistry · Question 715

Which hydroxide is least soluble in water?

  1. LiOH
  2. NaOH
  3. KOH
  4. RbOH
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Correct answer: A

LiOH

Solubility of Group 1 hydroxides generally increases down the group; LiOH is least soluble here.

Chemistry · Question 716

Which alkali metal forms a normal oxide when burned in oxygen?

  1. Lithium
  2. Sodium
  3. Potassium
  4. Rubidium
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Correct answer: A

Lithium

Lithium forms Li₂O; heavier alkali metals preferentially form peroxides or superoxides.

Chemistry · Question 717

Which carbonate releases carbon dioxide on heating?

  1. Li₂CO₃
  2. Na₂CO₃
  3. K₂CO₃
  4. All three
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Correct answer: A

Li₂CO₃

Lithium carbonate decomposes to Li₂O and CO₂; sodium and potassium carbonates are thermally stable under ordinary laboratory heating.

Chemistry · Question 718

Which alkali-metal hydroxide decomposes most readily on heating?

  1. NaOH
  2. KOH
  3. LiOH
  4. RbOH
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Correct answer: C

LiOH

Lithium hydroxide is less thermally stable and decomposes to Li₂O and water.

Chemistry · Question 719

Which compound is a constituent of baking powder?

  1. Na₂CO₃
  2. Na₂SO₄
  3. NaHCO₃
  4. K₂CO₃
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Correct answer: C

NaHCO₃

Sodium hydrogen carbonate releases carbon dioxide when the baking powder reacts.

Chemistry · Question 720

Which mineral is an ore/source of potassium?

  1. Carnallite
  2. Cryolite
  3. Bauxite
  4. Dolomite
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Correct answer: A

Carnallite

Carnallite, KMgCl₃·6H₂O, is an important potassium mineral.