Some basic concepts of chemistry practice · Mixed difficulty

Option B ($6.02 \times {10^{19}}$) is correct because it's calculated by finding the mass of sulfur in 16g of biomolecule and then converting it to the number of sulfur atoms.

Option C (34 g) is correct because it is the mass of $H_2S$ required to precipitate 63.5 g of $Cu^{2+}$ based on stoichiometry.

Option B (Dalton, Avogadro respectively) is correct because Dalton introduced the concept of the atom, and Avogadro contributed significantly to the understanding of molecules.

Option D (Assertion is false, Reason is true) is correct. The assertion is false because the milliequivalents of acid and base are equal, resulting in a neutral solution. The reason is true because the acidity of the solution depends on the relative milliequivalents of acid and base.

Option D ($3 M / 4$) is correct because the equivalent weight is calculated by considering both the oxidation and reduction processes in the disproportionation reaction and then averaging the results.

Option A (107.9) is correct because the molar mass of Ag (Silver) is approximately 107.9 g/mol, meaning one mole of Ag weighs 107.9 grams.

Option A (1000 g of the solvent) is correct because a molal solution is defined as one mole of solute dissolved in 1000 grams (1 kg) of solvent.

Option A (5) is correct because Mass percent, Mole fraction, Molarity, ppm, and Molality are all units used to express the concentration of solutions.

Option D (Both (b) and (c )) is correct because milliequivalents can be calculated using both $N \times V_{\text{in mL}}$ and $\frac{{\text{wt}}}{{\text{Eq.wt}}} \times 1000$.

Option A (4.13 g) is correct because it is calculated based on the stoichiometry of the redox reaction and the equivalent weights of the reactants.

Option A is correct because it correctly orders the masses from least to greatest: Nitrogen atom < Oxygen molecule < 1e-10 g Oxygen < 1e-10 g Copper.

Option D (Both X & Y neither precise nor accurate, Z both precise and accurate) is correct because X and Y's results are scattered and far from the true value, while Z's results are close to each other and the true value.

Option C ($1: 4$) is correct because the formula $\mathrm{Sn}_{4.4} \mathrm{O}_8$ implies that the average oxidation state of Sn is slightly above +2, and the ratio of Sn(II) to Sn(IV) can be calculated based on charge balance.

Option A (One litre of solution is one molar) is correct because a solution containing the formula weight of a substance in one liter is a 1 M solution.

Option B (4:1) is correct because the volume decrease in KOH solution corresponds to CO2, and the remaining gas is CO. The ratio of formic acid to oxalic acid is then determined from the amounts of CO and CO2 produced.

Option D ($C{r_2}{O_3} + 2Al\xrightarrow{\Delta }A{l_2}{O_3} + 2Cr$) is correct because aluminum displaces chromium from its oxide, which is a metal displacement reaction.

Option D is correct because $Fe^{2+}$ ions are typically green, and $Fe^{3+}$ ions are typically yellow in solution.

Option D ($2.5 \,\mathrm{mol} \,\mathrm{Au}$) is correct because it contains the smallest number of atoms, calculated as 2.5 mol * 1 atom/mol = 2.5 * Avogadro's number of atoms.

The correct answer is C (Multiple proportion) because carbon and oxygen form two different compounds, CO and CO2, where the ratio of oxygen masses combining with a fixed mass of carbon is a simple whole number.

Option D ($0.16\,g$) is correct because the weight of oxygen is calculated using the molar mass and the volume at NTP.

Option D (All of these) is correct because all the statements are true: 28g CO contains 12g C and 16g O, one mole of CO reacts completely with half mole of O2 to form CO2, and N2 and CO have the same molar mass (28 g/mol).

Option D (Both Assertion and Reason are correct but Reason is not correct explanation of Assertion) is correct because both statements are true, but the reason doesn't explain the assertion.

Option A (4.4) is correct because the mass of $CO_2$ produced from the decomposition of $CaCO_3$ is 4.4g, following stoichiometry.

Option A (Assertion is true, Reason is true and Reason is correct explanation for Assertion) is correct because the equivalent weight is indeed the molecular weight divided by the number of electrons lost or gained, and both the assertion and reason are correct and related.

The correct answer is D (Mass of product = Mass of reactant) because according to the law of conservation of mass, mass is neither created nor destroyed in a chemical reaction.

Option D is correct because both the assertion and the reason are false. The activity of a radioactive element depends on its specific activity and amount, not its chemical state.

Option A (1 L) is correct because the volume occupied by 1g of the gas at NTP is calculated using the vapor density and molar volume.

Option B (11.2 litre) is correct because it is half the molar volume at NTP, corresponding to half a mole of acetylene.

Option C is correct because disproportionation involves a single element undergoing both oxidation and reduction, which is not happening in option C where electrons are simply added to MnO4-.

Option B (At. wt.) is correct because the atomic weight of an element is a constant property, while valence and equivalent weight can vary depending on the chemical context.