1.简单
What kind of carbon–carbon bonds do alkanes contain?
- AIonic bonds
- BAt least one double bond
- CAt least one triple bond
- DOnly single bonds
2.简单
Boyle's law describes the relationship between which two properties of a gas, at constant temperature?
- APressure and temperature
- BPressure and volume
- CMass and volume
- DVolume and temperature
3.简单
According to the Arrhenius definition, what does a base produce in water?
- AHydrogen ions (H⁺)
- BHydroxide ions (OH⁻)
- CCarbonate ions (CO₃²⁻)
- DChloride ions (Cl⁻)
4.中等
Why does keeping food in a refrigerator slow down spoilage?
- ACold air contains no oxygen
- BCold temperatures add preservatives to the food
- CLower temperatures slow down chemical and microbial reactions
- DLower temperatures raise the activation energy of every reaction
5.中等
Which substance is a non-electrolyte when dissolved in water?
- AGlucose
- BHydrochloric acid
- CPotassium chloride
- DSodium chloride
6.中等
A room is at 25 °C. What is this temperature in kelvin?
- A298 K
- B248 K
- C−248 K
- D77 K
7.困难
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
8.困难
What is a triglyceride made of?
- AOne fatty acid joined to three glycerol molecules
- BThree glucose molecules joined together
- COne glycerol molecule joined to three fatty acids
- DThree amino acids joined by peptide bonds
答案
- 1. D · Only single bonds
- 2. B · Pressure and volume
- 3. B · Hydroxide ions (OH⁻)
- 4. C · Lower temperatures slow down chemical and microbial reactions
- 5. A · Glucose
- 6. A · 298 K
- 7. D · Dissolving is endothermic; the dissolving salt took heat from the water
- 8. C · One glycerol molecule joined to three fatty acids
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