1.Dễ
In a chemical equation, what are the reactants?
- AThe starting substances, written to the left of the arrow
- BThe numbers written in front of each formula
- CThe new substances formed, written to the right of the arrow
- DThe catalysts written above the arrow
2.Dễ
What does the double arrow (⇌) in a chemical equation show?
- AThe reaction is very fast
- BThe reaction needs a catalyst
- CThe reaction releases heat
- DThe reaction is reversible
3.Dễ
What is the change from a liquid to a solid called?
- AEvaporation
- BFreezing
- CCondensation
- DMelting
4.Trung bình
A bag of 5% (w/v) glucose solution (called 5% dextrose in the US) contains 5 g of glucose per 100 mL. How many grams of glucose are in 1 L?
- A5 g
- B0,5 g
- C50 g
- D500 g
5.Trung bình
What is 380 mmHg in atmospheres?
- A0,5 atm
- B380 atm
- C0,38 atm
- D2 atm
6.Trung bình
How many lone (non-bonding) pairs of electrons are on the oxygen atom in a water molecule?
- A0
- B1
- C4
- D2
7.Khó
Mẫu nào chứa số nguyên tử lớn nhất?
- A1 mol CH₄
- B1 mol He
- C1 mol H₂O
- D1 mol O₂
8.Khó
A salt is dissolved in water in an insulated cup, and the water temperature falls from 25 °C to 20 °C. Which statement is correct?
- ADissolving is endothermic; the water took heat from the salt
- BNo energy change occurred, because the temperature fell
- CDissolving is exothermic; the dissolving salt released heat into the water
- DDissolving is endothermic; the dissolving salt took heat from the water
Đáp án
- 1. A · The starting substances, written to the left of the arrow
- 2. D · The reaction is reversible
- 3. B · Freezing
- 4. C · 50 g
- 5. A · 0,5 atm
- 6. D · 2
- 7. A · 1 mol CH₄
- 8. D · Dissolving is endothermic; the dissolving salt took heat from the water
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