exam questions Flashcards
Describe a test to distinguish between sodium oxide and phosphorus oxide.
→ react with water
→ add litmus paper
→ turns blue with Na₂O & red with P₄O₁₀
Equation for reaction of excess magnesium oxide with
phosphoric acid.
3 MgO + 2H₃PO₄ → Mg₃(PO₄)₂ + 3H₂O
Describe a test to distinguish between potassium nitrate and potassium sulfate.
→ Ba(OH)₂
→ no reaction with KNO3
→ white ppt with K2SO4
Describe a test to distinguish between magnesium chloride and aluminium chloride.
→ NaOH
→ both forms white ppt
→ Al(OH)3 is amphoteric so dissolves in excess NaOH
State the meaning of the term periodicity.
repeating trend in physical and chemical properties of elements in the periodic table
Give an equation for the reaction between solid sodium chloride and concentrated sulphuric acid.
NaCl + H₂SO₄ → NaHSO₄ + HCl
Test for ammonia gas.
turns red damp litmus paper blue
State one other observation when Na2CO3(aq) is added to a solution containing [Al(H₂O)₆]³⁺ (aq) ions.
bubbles/effervescence
Explain, with the use of an equation, why a solution containing [Al(H₂O)₆]³⁺ has a pH <7.
[Al(H₂O)₆]³⁺ + H₂O ⇌ [Al(H₂O)5(OH)]²⁺ + H₃O⁺
→ Al3+ has a high charge density
→ weakens the OH bond (in water) releasing H+ ions
State one observation when solid sodium chloride reacts with concentrated sulfuric acid.
misty/white fumes
State what is observed when aqueous chlorine is added to sodium bromide solution and give an ionic equation for the reaction.
Cl2 + 2Br– → 2Cl– + Br2
yellow solution
State the role of chloride ions in the reaction between solid sodium chloride and concentrated sulfuric acid.
base
Suggest what substance might be present in the air to cause the pH to change in a solution left open in air.
CO2
causes pH to decrease as acidic gas
