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自然科學
國小五六年級
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1
What is the correct definition of a coefficient in a chemical equation?
A
A small number written after a chemical symbol to show the number of atoms in a molecule.
B
A number that shows the total mass of a compound.
C
A symbol that shows the state of matter of a substance.
D
A number placed in front of a chemical formula to show how many molecules or formula units are involved.
2
In the chemical equation H₂ + O₂ → H₂O, how many oxygen atoms are on the reactant side?
A
4
B
1
C
3
D
2
3
When balancing a chemical equation, which of the following should you change?
A
The subscripts in the chemical formulas.
B
The coefficients in front of the chemical formulas.
C
The state symbols (s, l, g, aq).
D
The chemical symbols themselves.
4
After balancing the equation CH₄ + 2O₂ → CO₂ + 2H₂O, how can you verify that the equation is balanced?
A
Check that the total number of molecules is the same on both sides.
B
Check that the number of each type of atom is the same on both sides.
C
Check that the coefficients are all equal to 1.
D
Check that the sum of coefficients on the left equals the sum on the right.