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Which statement is the Brønsted–Lowry definition of a base?
A proton acceptor A proton donor A substance that always contains OH− An electron-pair acceptor In the forward reaction NH₃ + H₂O → NH₄⁺ + OH⁻, which reactant acts as the Brønsted–Lowry acid?
$\ce{NH3}$ $\ce{H2O}$ $\ce{NH4+}$ $\ce{OH-}$ What is the conjugate base of H₂PO₄⁻?
HPO₄²⁻ H₃PO₄ PO₄³⁻ It has no conjugate base, because it is already an anion. Which statement correctly compares acid strength and concentration?
Strength describes dissociation; concentration describes amount per unit volume Strength describes amount per unit volume; concentration describes dissociation Strength and concentration both describe the fraction dissociated Strength and concentration both describe amount per unit volume At the same temperature and concentration, why does aqueous HCl normally have a lower pH than a weak monoprotic acid?
HCl is more extensively dissociated, producing a higher [H⁺] HCl has a lower [H⁺] because it is more extensively dissociated The weak acid is fully dissociated, producing a higher [H⁺] Equal acid concentrations must produce equal [H⁺] What is the pH of 1.00 × 10⁻³ mol dm⁻³ HNO₃(aq)?
At 25 °C, what is the pH of 1.00 × 10⁻² mol dm⁻³ NaOH(aq)?
An aqueous solution contains dissolved Ca(OH)₂ at 5.00 × 10⁻³ mol dm⁻³. Assuming complete dissociation, what is [OH⁻]?
1.00 × 10⁻² mol dm⁻³ 5.00 × 10⁻³ mol dm⁻³ 2.50 × 10⁻³ mol dm⁻³ 2.00 × 10⁻² mol dm⁻³ A strong acid–weak base titration has a steep pH change from 3.2 to 6.0 near equivalence. Which indicator transition range lies wholly within this region?
pH 3.5–5.0 pH 6.5–8.0 pH 8.5–10.0 pH 10.5–12.0 Why is a visual indicator generally unsuitable for a weak acid–weak base titration?
There is no sufficiently steep pH change near equivalence The reaction cannot occur Both solutions are always colourless The equivalence point is always pH 7 How does an HA/A− buffer respond to a small amount of added H+?
A− reacts with H+ to form HA HA releases all of its H+ immediately HA reacts with H⁺ to form more A⁻ A− produces additional H+ How does an HA/A− buffer respond to a small amount of added OH−?
HA reacts with OH− to form A− and H2O A− reacts with OH− to form H+ The added OH⁻ reacts mainly with A⁻ HA releases OH⁻ and increases the added base What does ocean acidification mean?
A decrease in ocean pH All seawater has pH below 7 Complete removal of carbonate ions An increase in ocean pH Why can increasing atmospheric CO₂ lower ocean pH?
More dissolved CO₂ forms carbonic acid that releases H⁺ More dissolved CO₂ consumes H⁺ to form HCO₃⁻ CO₂ dissolves without reacting with water, so [H⁺] increases CO₂ reacts with water to release OH⁻ instead of H⁺ Which pair can form an acidic buffer when both components are present in comparable concentrations in water?
CH3CO2H and CH3CO2− HCl and NaCl NaOH and NaCl HNO3 and KNO3 Which statement gives the Arrhenius definition of an acid?
It produces H+(aq) in water It accepts H+ in any solvent It donates an electron pair It produces electrons in water Two weak monoprotic acids are separately dissolved in water at the same analytical concentration and temperature. What does a larger Kₐ indicate?
A greater fraction of the acid dissociates A lower analytical concentration of the acid A greater fraction of the acid remains undissociated A lower equilibrium hydrogen-ion concentration Which expression defines the ionic product of water?
Kw = [H+][OH−] Kw = [H+]/[OH−] Kw = [H2O][OH−] Kw = −log10[H+]