Basic Laboratory Technique

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1. CSCA Chemistry April 2026 Past Paper
   Among the following gases prepared in the laboratory, the one that cannot be collected over water and can only be collected by downward displacement of air is ( ).
   • A. $\mathrm{O_{2}}$
   • B. $\mathrm{NH_{3}}$
   • C. $\mathrm{H_{2}}$
   • D. $\mathrm{CO_{2}}$
   Lihat jawaban & pembahasan

   Jawaban: B

   Answer: B $\mathrm{NH_{3}}$ is extremely soluble in water and less dense than air, so it can only be collected by downward displacement of air.
   Kerjakan CSCA Chemistry April 2026 Past Paper lengkap — berwaktu & dinilai
2. CSCA Chemistry March 2026 Past Paper
   Which gas can be collected by both water displacement and downward air displacement?
   • A．$\mathrm { H } _ { 2 }$
   • B．$\mathrm { CO } _ { 2 }$
   • C．O₂
   • D．$\mathrm { SO } _ { 2 }$
   Lihat jawaban & pembahasan

   Jawaban: A

   $\mathrm { H } _ { 2 }$ : lighter than air (downward displacement) + insoluble (water displacement). Answer: A.
   Kerjakan CSCA Chemistry March 2026 Past Paper lengkap — berwaktu & dinilai