Neutralisation: select products and balance salt charges
| English | 中文 | Pinyin |
|---|---|---|
| alkali/ˈælkəlaɪ/ | 可溶性碱 | kě róng xìng jiǎn |
| base/beɪs/ | 碱性物质 | jiǎn xìng wù zhì |
What would explain this observation?
- Copper oxide with sulfuric acid gives copper sulfate and water. Changing the acid to nitric acid changes the salt’s negative ion, even though copper stays the positive ion.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Acid plus a metal oxide or hydroxide gives salt and water. Acid plus a metal carbonate gives salt, water and carbon dioxide. An alkali 可溶性碱 is a soluble base 碱性物质; some bases are insoluble. Hydrochloric acid supplies chloride salts, nitric acid nitrate salts and sulfuric acid sulfate salts. The base, alkali or carbonate supplies the positive ion.
- base: A substance that neutralises an acid; it need not be soluble; alkali: A soluble base producing hydroxide ions in aqueous solution.
Which products form when calcium carbonate reacts with hydrochloric acid?
Use charges to make a neutral formula: Cu²⁺ and SO₄²⁻ give CuSO₄; Mg²⁺ and NO₃⁻ give Mg(NO₃)₂. CuO + H₂SO₄ → CuSO₄ + H₂O is balanced. CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂ has two chloride ions per calcium ion and one carbon dioxide molecule per carbonate formula unit.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Use charges to make a neutral formula: Cu²⁺ and SO₄²⁻ give CuSO₄; Mg²⁺ and NO₃⁻ give Mg(NO₃)₂. CuO + H₂SO₄ → CuSO₄ + H₂O is balanced. CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂ has two chloride ions per calcium ion and one carbon dioxide molecule per carbonate formula unit.
- Identify the acid first, then the positive ion and required ratio. Use brackets when more than one polyatomic ion is needed, keeping the nitrate or sulfate group intact. Confirm atom counts in the full equation. Observe carbon dioxide with the approved limewater test where appropriate, rather than treating all bubbles as hydrogen.
Which two habits make the investigation or model in this case more defensible?
Identify the acid first, then the positive ion and required ratio. Use brackets when more than one polyatomic ion is needed, keeping the nitrate or sulfate group intact. Confirm atom counts in the full equation. Observe carbon dioxide with the approved limewater test where appropriate, rather than treating all bubbles as hydrogen.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: aluminium ions Al³⁺ combine with sulfate SO₄²⁻. Two aluminium ions supply +6 and three sulfates supply −6, giving Al₂(SO₄)₃. The formula contains two Al, three S and twelve O atoms. This formula exercise uses supplied ions and does not require conducting a reaction with aluminium oxide in class.
How many nitrate ions NO₃⁻ balance the charge of four Mg²⁺ ions? Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
How many nitrate ions NO₃⁻ balance the charge of four Mg²⁺ ions?
The result is 8 ions. Known: aluminium ions Al³⁺ combine with sulfate SO₄²⁻. Two aluminium ions supply +6 and three sulfates supply −6, giving Al₂(SO₄)₃. The formula contains two Al, three S and twelve O atoms. This formula exercise uses supplied ions and does not require conducting a reaction with aluminium oxide in class.
Check the conclusion and its limits
- Water is a product of oxide/hydroxide neutralisation, while carbonate neutralisation also produces carbon dioxide. A base need not dissolve in water to react with acid. A salt’s name depends on both ions, and the polyatomic-ion subscript inside its own formula must not be altered to balance charge.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Every base must dissolve in water to neutralise an acid. This claim is false: Water is a product of oxide/hydroxide neutralisation, while carbonate neutralisation also produces carbon dioxide. A base need not dissolve in water to react with acid. A salt’s name depends on both ions, and the polyatomic-ion subscript inside its own formula must not be altered to balance charge.
Neutralisation: select products and balance salt charges: Use charges to make a neutral formula: Cu²⁺ and SO₄²⁻ give CuSO₄; Mg²⁺ and NO₃⁻ give Mg(NO₃)₂. CuO + H₂SO₄ → CuSO₄ + H₂O is balanced. CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂ has two chloride ions per calcium ion and one carbon dioxide molecule per carbonate formula unit.
Every base must dissolve in water to neutralise an acid.
Water is a product of oxide/hydroxide neutralisation, while carbonate neutralisation also produces carbon dioxide. A base need not dissolve in water to react with acid. A salt’s name depends on both ions, and the polyatomic-ion subscript inside its own formula must not be altered to balance charge.
A substance that neutralises an acid; it need not be soluble: write the technical term.
base means A substance that neutralises an acid; it need not be soluble.