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自然科學
國小五六年級
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1
In the chemical equation for photosynthesis, 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, which substances are the reactants?
A
CO₂ and H₂O
B
C₆H₁₂O₆ and O₂
C
CO₂ and C₆H₁₂O₆
D
H₂O and O₂
2
What does the arrow (→) in a chemical equation represent?
A
The addition of two substances
B
The speed at which the reaction occurs
C
The direction of the reaction, showing reactants changing into products
D
The substances that are used up
3
A student writes the equation: H₂ + O₂ → H₂O. Which of the following best explains why this equation is not balanced?
A
Water is not a product in this reaction.
B
There are more oxygen atoms on the reactant side than on the product side.
C
The reactants and products are on the wrong sides.
D
The plus sign should be a minus sign.
4
In the equation 2H₂ + O₂ → 2H₂O, what does the coefficient '2' in front of H₂ indicate?
A
There are two molecules of hydrogen gas reacting.
B
The hydrogen is a product.
C
The reaction happens twice as fast.
D
There are two hydrogen atoms in each molecule.