Combined Science — Chemistry Flashcards
6 cards from real O-LEVEL practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Combined Science — Chemistry flashcards as text
What is the name of the process by which a solid changes directly into a gas?
Answer: Sublimation
Sublimation is the process by which a solid changes directly into a gas without passing through the liquid phase, e.g., dry ice (solid CO₂).
In electrolysis, where does oxidation occur?
Answer: At the anode
Oxidation occurs at the anode (positive electrode). The mnemonic OIL RIG helps: Oxidation Is Loss; Reduction Is Gain.
Which element is represented by the symbol 'Na'?
Answer: Sodium
'Na' is the chemical symbol for sodium, derived from the Latin word 'Natrium'.
What is the empirical formula of a compound with 2 carbon, 6 hydrogen, and 2 oxygen atoms?
Answer: CH₃O
Divide all subscripts by the HCF (2): C₂H₆O₂ → CH₃O. The empirical formula is CH₃O.
Which gas is used in the Haber Process to make ammonia?
Answer: Nitrogen and hydrogen
The Haber Process combines nitrogen (from air) and hydrogen (from natural gas) at high temperature and pressure with an iron catalyst to make ammonia.
What colour does litmus paper turn in an acidic solution?
Answer: Red
Blue litmus paper turns red in acidic solutions (pH below 7). Red litmus turns blue in alkaline solutions.
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