1.Dễ
How is percent yield calculated?
- A(Mass of reactants ÷ mass of products) × 100
- BActual yield − theoretical yield
- C(Actual yield ÷ theoretical yield) × 100
- D(Theoretical yield ÷ actual yield) × 100
2.Dễ
Chất nào là một base?
- AHydrochloric acid (HCl)
- BGiấm (acetic acid)
- CNước chanh (citric acid)
- DSodium hydroxide (NaOH)
3.Dễ
What is activation energy?
- AThe energy needed to melt a solid
- BThe total energy released once the reaction has finished
- CThe minimum energy reacting particles need for a reaction to happen
- DThe energy stored in the products
4.Trung bình
Rubbing alcohol evaporates faster than water at room temperature. What does this suggest?
- AIt has a higher boiling point than water
- BIts intermolecular forces are stronger than water's
- CIts molecules are heavier than water molecules
- DIts intermolecular forces are weaker than water's
5.Trung bình
Phần trăm khối lượng muối trong dung dịch pha từ 15 g muối và 135 g nước là bao nhiêu?
- A10%
- B11%
- C15%
- D90%
6.Trung bình
Which list is in order from smallest to largest mass?
- AMilligram, gram, kilogram
- BMilligram, kilogram, gram
- CKilogram, gram, milligram
- DGram, milligram, kilogram
7.Khó
Starch and cellulose are both made entirely of glucose units, yet humans can digest starch but not cellulose. Why?
- ACellulose is really made of amino acids, not glucose, so stomach acid cannot break it
- BThe glucose units are linked differently, and humans lack an enzyme to break cellulose's links
- CStarch contains nitrogen, which makes it easier to digest
- DCellulose dissolves in water, so it is lost from the gut
8.Khó
Why are the radioactive tracers used for medical imaging usually chosen to have short half-lives?
- AShort half-life isotopes are not radioactive
- BThey stay active for many years, so a single dose can be used for every future scan
- CThey give a strong signal for imaging but leave the body's tissues exposed only briefly
- DThey emit only alpha particles, which are harmless inside the body
Đáp án
- 1. C · (Actual yield ÷ theoretical yield) × 100
- 2. D · Sodium hydroxide (NaOH)
- 3. C · The minimum energy reacting particles need for a reaction to happen
- 4. D · Its intermolecular forces are weaker than water's
- 5. A · 10%
- 6. A · Milligram, gram, kilogram
- 7. B · The glucose units are linked differently, and humans lack an enzyme to break cellulose's links
- 8. C · They give a strong signal for imaging but leave the body's tissues exposed only briefly
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