ONE-EIGHTH STAGE 2023
Mawuli School: 52 points
Amaniampong SHS: 37 points
St. Catherine SHS: 31 points
ROUND 4 - TRUE OR FALSE
PREAMBLE
Statements concern binary compounds.
1. A binary compound is composed of exactly two atoms from different elements.
ANSWER: FALSE
EXPLANATION:
A binary compound has exactly two different ELEMENTS, not necessarily just two atoms (e.g. H$_2$O has 3 atoms but only 2 elements).
2. A binary compound is composed of two or more different elements.
ANSWER: FALSE
EXPLANATION:
"Binary" specifically means exactly two elements, not "two or more".
3. A binary compound is composed of exactly two elements, which may be the same or different.
ANSWER: FALSE
EXPLANATION:
The two elements must be different — a substance made of only one element (like O$_2$) is not a compound at all.
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PRACTICE QUESTIONS
PREAMBLE 1
The following statements concern binary compounds.
1. Sodium chloride is a binary compound.
ANSWER: TRUE
EXPLANATION:
It contains exactly two elements, sodium and chlorine.
2. Sodium hydroxide is a binary compound.
ANSWER: FALSE
EXPLANATION:
NaOH contains three elements: sodium, oxygen and hydrogen.
3. Water is a binary compound.
ANSWER: TRUE
EXPLANATION:
It contains exactly two elements, hydrogen and oxygen.
PREAMBLE 2
The following statements concern the classification of substances.
1. Brass is a compound.
ANSWER: FALSE
EXPLANATION:
Brass is an alloy (a mixture) of copper and zinc; its composition can vary.
2. Carbon dioxide is a compound.
ANSWER: TRUE
EXPLANATION:
It contains carbon and oxygen chemically combined in a fixed ratio.
3. Sea water is a mixture.
ANSWER: TRUE
EXPLANATION:
It is water with various dissolved salts in varying amounts.