NESA Chemistry Properties of Acids and Bases

Ammonia ($NH_3$) acts as a weak base because it accepts protons, rather than donating multiple protons like a polyprotic acid.

Ammonium phosphate is an ionic salt composed of ammonium and phosphate ions, not a polyprotic acid molecule.

Acetic acid ($CH_3COOH$) is a monoprotic acid because only the single hydrogen in the carboxyl group ($-COOH$) is ionizable.

The Brønsted-Lowry theory successfully explains neutralization reactions between strong acids and strong bases through the transfer of a proton from the acid (or hydronium ion) to the base (or hydroxide ion).

The concept of conjugate acid-base pairs in the Brønsted-Lowry theory is actually based entirely on the transfer of protons, rather than being an alternative to it.

The Brønsted-Lowry theory effectively explains the acidity and basicity of salts through hydrolysis, where the constituent ions of the salt act as proton donors or acceptors when interacting with water.

Acid-base indicators respond to changes in hydrogen ion concentration, not electron transfer. Indicators that act as oxidising or reducing agents are known as redox indicators.

Indicators change colour over a specific pH range (typically spanning about 2 pH units), rather than at one exact pH value.

If indicators were strong acids or bases, they would completely dissociate in solution, preventing the reversible equilibrium shift needed to produce a colour change.

This describes a Brønsted–Lowry base, not an acid. Acids donate protons, whereas bases accept them.

While acids do donate protons, the specific term for the species formed after the loss of a proton is the "conjugate base," making Option D the more precise and standard definition.

Acids donate protons rather than accepting them. Additionally, when a species accepts a proton, it forms a conjugate acid, not a conjugate base.

This condition implies the concentration of the indicator anion equals the hydrogen ion concentration, which is not the general definition for the color change midpoint.

This condition defines a neutral solution ($\text{pH} = 7$ at $25^\circ\text{C}$), whereas indicators change color at specific pH ranges determined by their $\text{pK}_{\text{In}}$ values, not necessarily at neutrality.

There is no theoretical relationship equating the concentration of the undissociated indicator to the hydroxide ion concentration that defines the midpoint of the color transition.

This value is obtained by dividing the actual yield (3.5 mol) by the initial moles of ethanoic acid (8.0 mol), neglecting the 2:1 stoichiometric ratio which dictates the theoretical yield is half the moles of the acid.

This calculation incorrectly identifies magnesium carbonate as the limiting reactant. Since magnesium carbonate is in excess, the theoretical yield should be based on ethanoic acid.

This option implies the actual yield equals the theoretical yield, but 3.5 moles is less than the calculated theoretical yield of 4.0 moles.

While $HCO_3^-$ does donate a proton, the overall process involves the condensation of chromate into dichromate, making it a more complex reaction rather than a simple Brønsted-Lowry acid-base proton transfer.

$NaOH$ provides the hydroxide ion ($OH^-$), which accepts a proton from the carboxylic acid. Therefore, it acts as a Brønsted-Lowry base, not an acid.

$CH_3NH_2$ accepts a proton from $HClO_3$ to form $CH_3NH_3^+$. Because it accepts a proton, it is acting as a Brønsted-Lowry base.

This is incorrect because the reaction is a redox process, not a simple acid-base proton transfer. Furthermore, reactant collisions (statement i) are essential.

This is incorrect because copper atoms are oxidized (losing electrons to go from an oxidation state of 0 to +2), not reduced.

This is incorrect because copper is oxidized rather than reduced, making statement iii false. Additionally, the primary mechanism is redox, not proton donation/acceptance.

Incorrect. While statement (i) is true, statement (ii) is also correct because acid-base indicators are typically weak acids or weak bases.

Incorrect. Statement (iii) is false because indicators must react with the acid or base in the solution to change color, though they are used in small amounts.

Incorrect. Statements (iii) and (iv) are false. Indicators do react with the reactants, and they must be used in very small volumes so they do not consume a significant amount of the titrant.

This equilibrium determines the concentration of carbonate ions ($CO_3^{2-}$). Increased ocean acidity shifts this reaction to the left, reducing the carbonate available for marine organisms to build strong shells.

This reaction shows carbon dioxide dissolving in water to form carbonic acid, which is the primary driver of ocean acidification that ultimately impairs shell building.

This reaction shows the dissociation of carbonic acid into bicarbonate and hydronium ions, which increases ocean acidity and leads to a reduction in the carbonate ions needed for shell building.