Use a copy of the Periodic Table where you need one.
A green powder is added to dilute hydrochloric acid. It fizzes and the gas turns limewater milky. What type of substance is the powder?
Source: Learners' Alley, Acids and Bases slides
Which pair of substances gives off ammonia when heated together?
Source: Learners' Alley, Acids and Bases slides
Solution P has pH 2 and solution Q has pH 5. Which statement is correct?
Source: Learners' Alley, Acids and Bases slides
Which element forms an oxide that dissolves in water to give a solution with a pH below 7?
Source: Learners' Alley, Acids and Bases slides
Answer these questions about acids, alkalis and oxides.
Source: Learners' Alley, Acids and Bases slides
An aqueous solution has a pH value of 1. What information does this fact imply about the ions present in the solution?
| concentration of H+ ions | concentration of OH− ions | |
|---|---|---|
| A | high | low |
| B | high | none |
| C | low | high |
| D | low | none |
Source: 2023 HYSS Sec 3 End-of-Year P1 Q12
Which statement about an alkali is incorrect?
Source: 2023 HYSS Sec 3 End-of-Year P1 Q14
Which row correctly classifies the nature of these oxides?
| aluminium oxide | nitrogen dioxide | sodium oxide | |
|---|---|---|---|
| A | amphoteric | basic | acidic |
| B | basic | acidic | amphoteric |
| C | amphoteric | acidic | basic |
| D | acidic | amphoteric | basic |
Source: 2023 GESS Sec 3 End-of-Year P1 Q29
A farmer wishes to grow some ceanothus flowers. The pH of his soil is 5.1. Ceanothus flowers are known to grow best at around pH 7.2. Which substance should he add to his soil for the ceanothus to grow well?
Source: 2023 GESS Sec 3 End-of-Year P1 Q30
Both magnesium carbonate and magnesium oxide react with dilute sulfuric acid. In what way are both reactions the same?
Source: 2024 CHS Sec 3 End-of-Year Section A Q23
The table shows information about three indicators. Which colour would each indicator show if it were added separately to pure water?
| indicator | colour change | pH at which colour changes |
|---|---|---|
| methyl yellow | red to yellow | 3 |
| bromocresol green | yellow to blue | 5 |
| thymolphthalein | colourless to blue | 9 |
| methyl yellow | bromocresol green | thymolphthalein | |
|---|---|---|---|
| A | red | blue | blue |
| B | red | yellow | blue |
| C | yellow | blue | colourless |
| D | yellow | yellow | colourless |
Source: 2023 XMS Sec 3 WA3 Q5
Which equation suggests that a metal oxide, RO, behaves as an amphoteric oxide?
Source: 2024 SMSS Sec 3 End-of-Year P1 Q12
In an accident at a factory, some dilute acid was spilt. Which substance, when added in excess, removes the acid without leaving an alkaline solution?
Source: 2024 CHS Sec 3 End-of-Year Section A Q24
Choose from the following substances to answer the questions: Al2O3, NaCl, N2, Pb(NO3)2, SO2. Each substance may be used once, more than once or not at all.
Source: 2023 XMS Sec 3 WA3 Q6, adapted
Hydrochloric acid is a strong acid with pH 1 while ethanoic acid is a weak acid with pH 5.
Source: SJI 2020 Year 3 End-of-Year P2 B8(a)
Ca carbonate[1]
The gas is carbon dioxide, which only a carbonate gives with an acid. A metal gives hydrogen, and a metal oxide or an alkali gives no gas.
Bammonium sulfate and sodium hydroxide[1]
An alkali heated with an ammonium salt gives off ammonia. A has no alkali, C has no ammonium salt, and water is not an alkali.
BP has a higher concentration of H+ ions than Q.[1]
The lower the pH, the higher the concentration of H+ ions. Both solutions are acidic.
Csulfur[1]
Sulfur is a non-metal, so its oxide is acidic and dissolves to form an acid. Sodium oxide dissolves to form an alkali.
A substance that produces hydrogen ions, H+, in aqueous solution. [1]
H+(aq) + OH−(aq) → H2O(l) [1]
A strong acid is completely ionised in aqueous solution. [1]
A weak acid is only partially ionised in aqueous solution. [1]
Amphoteric, because it reacts with both acids and alkalis. [1]
AH+ high, OH− low[1]
pH 1 is strongly acidic, so the H+ concentration is high. Some OH− ions are still present, at a low concentration.
AIt reacts with a carbonate to form carbon dioxide.[1]
It is acids that react with carbonates to give carbon dioxide. Alkalis neutralise acids, give ammonia with ammonium salts and turn Universal Indicator blue.
Camphoteric, acidic, basic[1]
Aluminium oxide is one of the amphoteric oxides (with zinc oxide and lead(II) oxide). Nitrogen is a non-metal, so its oxide is acidic. Sodium is a metal, so its oxide is basic.
Acalcium hydroxide[1]
Calcium hydroxide (slaked lime) neutralises acidity in soil and raises the pH. Sodium hydroxide is an alkali that is too strong to use on soil.
DWater is a product.[1]
Carbonate + acid gives salt + water + carbon dioxide, and base + acid gives salt + water. Water is the product in both. Only the carbonate gives a gas, and neither is a soluble base.
Cyellow, blue, colourless[1]
Pure water has pH 7. That is above 3 (methyl yellow is yellow) and above 5 (bromocresol green is blue), but below 9 (thymolphthalein stays colourless).
BRO(s) + 2OH−(aq) → RO22−(aq) + H2O(l)[1]
Every metal oxide that is a base reacts with acids, as in A. A metal oxide that also reacts with an alkali (OH− ions), as in B, is amphoteric.
Dsolid calcium carbonate[1]
Calcium carbonate neutralises the acid, and the excess is an insoluble solid, so the solution is not left alkaline. Excess aqueous ammonia or sodium hydroxide leaves an alkaline solution, and ammonium nitrate does not remove acid.
Al2O3 [1]
SO2 [1]
A substance that ionises partially in water to form a low concentration of hydrogen ions. [1]
Add a reactive metal such as magnesium, or a carbonate such as sodium carbonate, to separate samples of each acid. [1]
Sulfuric acid gives more vigorous bubbling, or the solid disappears in a shorter time. [1]
So sulfuric acid is the strong acid and ethanoic acid is the weak acid. [1]