1993 年
化學 · 共 29 題 · 點擊選項即時核對答案
Which of the following pairs of atoms/ions has the same number of electrons ?
The elements, sodium to chlorine, in the third period of the Periodic Table show a gradual change in properties. Which of the following changes is correct ?
Directions: Q.5 and Q.6 refer to the following experiment: A silver coin, with a mass of 12.00 g, was dissolved completely in concentrated nitric acid. When excess potassium chloride solution was added to the resulting solution, 14.35 g of a white precipitate were obtained.
Which of the following equation correctly represents the reaction between silver and concentrated nitric acid ?
Directions: Q.5 and Q.6 refer to the following experiment: A silver coin, with a mass of 12.00 g, was dissolved completely in concentrated nitric acid. When excess potassium chloride solution was added to the resulting solution, 14.35 g of a white precipitate were obtained.
What is the percentage by mass of silver in the coin ? (Relative atomic masses: Cl = 35.5, Ag = 108)
CO₂(g) + CaCO₃(x) + H₂O(y) → Ca(HCO₃)₂(z) In the above chemical equation, which of the following combination is correct?
| x | y | z | |
|---|---|---|---|
| aq | l | aq | |
| s | aq | s | |
| s | l | s | |
| s | l | aq |
The molecular formula of a gaseous element X is X₂. If the relative atomic mass of X is 19, what is the number of molecules in 114 g of the gas ? (Avogadro's number = 6.022 × 10²³)
0.21 g of a gaseous hydrocarbon occupies 0.12 dm³ at room temperature and pressure. If this hydrocarbon has the empirical formula CH₂, what is its molecular formula? (Relative atomic masses: H = 1.0, C = 12.0; Molar volume of gas at room temperature and pressure = 24 dm³)
The following substances were burnt in oxygen and the products were mixed with water. Which of these substances would produce a resulting solution with the highest pH value?
A mixture contains copper powder and zinc powder. In order to remove the zinc powder, the mixture is heated with an acid and filtered. Which of the following acids should be used ?
The oxidation number of copper remains unchanged when