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自然科學
國小五六年級
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1
What does the chemical formula H₂O tell you about the elements present in water?
A
It contains only hydrogen.
B
It contains hydrogen and oxygen.
C
It contains hydrogen and ozone.
D
It contains helium and oxygen.
2
In the formula CO₂, what does the subscript '2' indicate?
A
There are 2 molecules of CO₂.
B
There are 2 total atoms in the molecule.
C
There are 2 carbon atoms.
D
There are 2 oxygen atoms.
3
Which of the following formulas has a 1:2 ratio of carbon atoms to oxygen atoms?
A
C₂O
B
CO
C
CO₂
D
C₂O₂
4
A model of a molecule shows 2 nitrogen atoms and 3 oxygen atoms. What is the chemical formula for this molecule?
A
N₂O₃
B
NO
C
N₂O
D
N₃O₂
5
Consider the formulas CH₄ and C₂H₆. Which statement correctly compares the ratio of carbon to hydrogen atoms in these two compounds?
A
CH₄ has a 1:4 ratio, while C₂H₆ has a 2:6 ratio, which simplifies to 1:3.
B
Both have the same ratio of carbon to hydrogen atoms.
C
CH₄ has a 4:1 ratio, while C₂H₆ has a 6:2 ratio.
D
CH₄ has a 1:4 ratio, while C₂H₆ has a 1:3 ratio.