Questions and Answers
What is the equation for the reaction of zinc and dilute sulfuric acid?
Copper (II) oxide can react with dilute sulfuric acid.
True
What is the purpose of adding excess zinc to dilute sulfuric acid?
To ensure all the acid has been completely used up.
What color does screened methyl orange turn when the solution is neutral?
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The reaction of an insoluble base with an acid produces a(n) __________ salt.
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What is the first step in preparing lead(II) sulfate from lead(II) carbonate?
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It is safe to react Group 1 metals with acids.
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Which process is followed to obtain copper(II) sulfate crystals?
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What do you need to do before using a pipette for titration?
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The process of heating a solution to obtain a hot __________ solution is crucial for crystallization.
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Study Notes
Preparation of Soluble Salts
- Reacting excess reactive metal (e.g., Mg, Zn, Fe) with an acid (HCl, HNO3, H2SO4) produces soluble salts.
- For example, zinc reacts with dilute sulfuric acid:
- Equation: Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g).
- Procedure includes:
- Add excess zinc to dilute sulfuric acid until effervescence stops to ensure complete reaction.
- Filter to remove unreacted zinc, obtaining a pure zinc sulfate solution.
- Heat the solution to boil off about 1/3 volume for saturation.
- Cool the solution for crystallization.
- Crystals are filtered, rinsed, and dried between filter papers.
- Do not use Group 1 metals due to explosive reactions with acids.
Preparation Using Insoluble Bases/Carbonates
- Adding an insoluble base (like MgO, CuO) or carbonate (e.g., MgCO3, CuCO3) to an acid (HCl, HNO3, H2SO4) produces soluble salts.
- For example, copper(II) oxide reacts with dilute sulfuric acid:
- Equation: CuO(s) + H2SO4(aq) → CuSO4(aq) + H2O(l).
- Steps:
- Mix excess copper(II) oxide or carbonate with gently heated dilute sulfuric acid.
- After completion of reaction, filter to remove excess unreacted material.
- Heat the solution to saturation, and then cool for crystallization.
- Rinse and dry the resulting crystals.
Titration for Soluble Bases and Carbonates
- A soluble base (like sodium hydroxide) reacts with an acid to form salts.
- Example reaction:
- 2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l).
- Procedure:
- Use a pipette for 25.0 cm³ of sodium hydroxide in a conical flask, add pH indicator.
- Add dilute sulfuric acid dropwise from a burette until the indicator shows a color change to denote neutralization.
- Record the volume of acid used at the endpoint.
- Repeat without indicator and mix the recorded amounts to avoid impurities in the salt.
- Heat the final solution for saturation and allow to cool for crystallization.
Preparation of Insoluble Salts through Precipitation
- Insoluble salts can be prepared using two soluble reactants containing the required cation and anion.
- Example: Lead(II) chloride formed from lead(II) nitrate and sodium chloride:
- Equation: Pb(NO3)2(aq) + 2NaCl(aq) → PbCl2(s) + 2NaNO3(aq).
- Steps:
- Combine the two solutions, allowing cation and anion to react and form the desired precipitate.
- Filter the mixture to collect the precipitate, rinsing to eliminate impurities.
- Dry the resulting insoluble salt between filter papers.
Method from Insoluble Compound
- Generating insoluble salts from insoluble compounds requires conversion to soluble salts before precipitation.
- Example: Lead(II) sulfate from lead(II) carbonate involves two steps:
- Step 1: PbCO3(s) + 2HNO3(aq) → Pb(NO3)2(aq) + CO2(g) + H2O(l).
- Step 2: Pb(NO3)2(aq) + H2SO4(aq) → PbSO4(s) + 2HNO3(aq).
- Procedure:
- Dissolve excess lead(II) carbonate in dilute nitric acid to produce soluble lead(II) nitrate.
- Filter to remove unreacted lead(II) carbonate, then mix the clear nitrate solution with dilute sulfuric acid for precipitation.
- Filter, rinse, and dry the resultant lead(II) sulfate.
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Description
Learn about the preparation of soluble salts through the reaction of excess metal with an acid, including the equation and procedure for zinc and dilute sulfuric acid.
