Revision questions for section 4

Alkali Metals and Halogens

100

 Which halogen can displace chlorine from potassium chloride solution?  

   A) Fluorine  

   B) Chlorine  

   C) Bromine  

   D) Iodine  

 **Answer:** A) Fluorine 

   **Explanation:** Fluorine is more reactive than chlorine and displaces it in a redox reaction.  

200

What is the product when sodium reacts with water?  

   A) Sodium oxide and hydrogen  

   B) Sodium hydroxide and oxygen  

   C) Sodium hydroxide and hydrogen  

   D) Sodium chloride and water  

   **Answer:** C) Sodium hydroxide and hydrogen  

300

  Explain why potassium is more reactive than lithium.  

   **Answer:** Potassium’s outermost electron is farther from the nucleus, reducing attraction and making electron loss easier.  

400

Write the balanced equation for chlorine displacing bromine from potassium bromide.  

   **Answer:** Cl₂ + 2KBr-- 2KCl + Br₂

500

 Describe the flame test result for copper(II) ions.  

 **Answer:** A blue-green flame is observed.  

Atmospheric Gases

100

 Which gas turns limewater cloudy?  

   A) Oxygen  

   B) Carbon dioxide  

   C) Nitrogen  

   D) Hydrogen  

   **Answer:** B) Carbon dioxide  

200

 What percentage of the atmosphere is oxygen?  

   A) 78%  

   B) 21%  

   C) 0.04%  

   D) 1%  

   **Answer:** B) 21%  

300

Why is acetic acid used in the iron wool rusting experiment?  

   **Answer:** To catalyze the reaction between iron and oxygen.  

400

Name the gas produced when sulfur burns in air.  

 **Answer:** Sulfur dioxide (SO₂ ).  

500

 Explain why magnesium oxide is slightly alkaline in water.  

  **Answer:** Magnesium oxide reacts with water to form magnesium hydroxide, a weak alkali.  

Metals and their Uses

100

  Which metal is used for galvanizing iron?  

   A) Copper  

   B) Zinc  

   C) Aluminium  

   D) Tin  

   **Answer:** B) Zinc  

200

 What property makes copper suitable for electrical wiring?  

   A) High density  

   B) Low melting point  

   C) Good conductivity  

   D) Brittleness  

   **Answer:** C) Good conductivity  

300

 Why is stainless steel resistant to corrosion?

   **Answer:** It contains chromium, which forms a protective oxide layer.  

400

Name an alloy of copper and state its use.  

 

 **Answer:** Bronze (copper + tin); used in statues and medals.  

500

   Explain the role of carbon in extracting iron from its ore.  

  **Answer:** Carbon reduces iron(III) oxide to iron by removing oxygen.  

Acids and Alkalis

100

   What color does phenolphthalein turn in alkaline solutions?  

   A) Pink  

   B) Yellow  

   C) Red  

   D) Blue  

   **Answer:** A) Pink  

200

   Which acid produces sulfate salts?  

   A) Hydrochloric acid  

   B) Nitric acid  

   C) Sulfuric acid  

   D) Ethanoic acid  

   **Answer:** C) Sulfuric acid  

300

 Write the ionic equation for the neutralization of sulfuric acid with sodium hydroxide.  

   **Answer:** 2H⁺ + 2OH^- ---2H₂O .

400

Name the products when hydrochloric acid reacts with calcium carbonate.  

   **Answer:** Calcium chloride, water, and carbon dioxide.  

500

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Making Salts

100

100 

100

200

   What is the purpose of evaporating the solution in salt preparation?  

   A) To neutralize the acid  

   B) To crystallize the salt  

   C) To increase pH  

   D) To remove impurities  

   **Answer:** B) To crystallize the salt  

300

   Why is excess base added when making a soluble salt from an acid and insoluble base?  

leaving no unreacted acid in the product.  

400

   Name two soluble hydroxides.  

   **Answer:** Sodium hydroxideNaOH, potassium hydroxide KOH.  

500

  Write the equation for the reaction between copper oxide and sulfuric acid.  

   **Answer:** CuO + H₂SO₄ --CuSO₄ + H₂O