Q8. An analysis of iron oxide shows that its formula is Fe1.903. What percentages of iron exists as

Q: What is the correct answer for CUET UG Chemistry Q8?

The correct answer is B. Let the formula be Fe(x)Fe(1.9-x)O3, where 'x' is the number of Fe3+ ions and '1.9-x' is the number of Fe2+ ions (assuming Fe++ refers to Fe2+).Total positive charge = 3(x) + 2(1.9-x) = 3x + 3.8 - 2x = x + 3.8Total negative charge from Oxygen = 3 * (-2) = -6For electrical neutrality, total positive charge + total negative charge = 0x + 3.8 - 6 = 0x - 2.2 = 0x = 2.2 (This implies 2.2 Fe3+ ions, but

Q: Q8. An analysis of iron oxide shows that its formula is Fe1.903. What percentages of iron exists as Fe3+ and Fe4+ ions: (a) Fe3+ = 82.98% and Fe++ = 17.02% (b) Fe3+ = 84.21% and Fe4+ = 15.79% (c)…

The correct answer is B. Let the formula be Fe(x)Fe(1.9-x)O3, where 'x' is the number of Fe3+ ions and '1.9-x' is the number of Fe2+ ions (assuming Fe++ refers to Fe2+).Total positive charge = 3(x) + 2(1.9-x) = 3x + 3.8 - 2x = x + 3.8Total negative charge from Oxygen = 3 * (-2) = -6For electrical neutrality, total positive charge + total negative charge = 0x + 3.8 - 6 = 0x - 2.2 = 0x = 2.2 (This implies 2.2 Fe3+ ions, but

Q: What are the options for this CUET UG Chemistry question?

A. (a) Fe3+ = 82.98% and Fe++ = 17.02% · B. (b) Fe3+ = 84.21% and Fe4+ = 15.79% · C. (c) Fe3+ = 15.79% and Fe4+ = 84.21% · D. (d) Fe3+ = 17.02% and Fe++ = 82.98%

Question

Q8. An analysis of iron oxide shows that its formula is Fe1.903. What percentages of iron exists as Fe3+ and Fe4+ ions:
(a) Fe3+ = 82.98% and Fe++ = 17.02%
(b) Fe3+ = 84.21% and Fe4+ = 15.79%
(c) Fe3+ = 15.79% and Fe4+ = 84.21%
(d) Fe3+ = 17.02% and Fe++ = 82.98%

FirstInTest · Accepted Answer

Let the formula be Fe(x)Fe(1.9-x)O3, where 'x' is the number of Fe3+ ions and '1.9-x' is the number of Fe2+ ions (assuming Fe++ refers to Fe2+).Total positive charge = 3(x) + 2(1.9-x) = 3x + 3.8 - 2x = x + 3.8Total negative charge from Oxygen = 3 * (-2) = -6For electrical neutrality, total positive charge + total negative charge = 0x + 3.8 - 6 = 0x - 2.2 = 0x = 2.2 (This implies 2.2 Fe3+ ions, but total Fe is 1.9. This suggests the Fe ions are Fe3+ and Fe2+ as commonly seen in non-stoichiometric iron oxides. The question states Fe3+ and Fe4+ ions which is unusual, assuming typo and it refers to Fe2+ for Fe++).Let's re-calculate assuming Fe3+ and Fe2+ as per common non-stoichiometric iron oxides, and that Fe4+ in the question means Fe2+:Let 'x' be the number of Fe3+ ions and 'y' be the number of Fe2+ ions.Total Fe atoms = x + y = 1.9Total positive charge = 3x + 2yTotal negative charge from 3 oxygen atoms = 3 * (-2) = -6For neutrality: 3x + 2y = 6From x + y = 1.9, we get y = 1.9 - x. Substitute into the charge balance equation:3x + 2(1.9 - x) = 63x + 3.8 - 2x = 6x = 6 - 3.8 = 2.2This result (x=2.2) is still inconsistent with total Fe of 1.9. This suggests there is an error in the question's 'Fe1.903' formula combined with the standard valencies or the provided options/solution logic. Let's follow the solution's specific calculation to reach their result.The solution uses 'Fe4+' which is generally not a stable oxidation state for iron. Assuming 'Fe4+' in the options and solution's initial setup is a typo for 'Fe2+'.Solution's explanation: "Suppose, the number of Fe3+ ions in one formula unit of Fe1.903 = x. So, number of Fe4+ ions per formula unit = (1.9 - x). The number of O atoms per formula unit of Fe1.903 = 3. In one formula unit of Fe1.903, total charge of cations = 3x + 4(1.9-x) and total charge of anions = -2x3 = -6. Since crystal of Fe1.903 is electrically neutral, the sum total positive charge and total negative charge is equal to zero. 3x + 4(1.9-x) -6 = 0 or x = 1.6."If we follow this interpretation (Fe3+ and Fe4+):Total positive charge = 3x + 4(1.9 - x) = 63x + 7.6 - 4x = 6-x = 6 - 7.6-x = -1.6 => x = 1.6 (number of Fe3+ ions)Number of Fe4+ ions = 1.9 - x = 1.9 - 1.6 = 0.3Percentage of Fe3+ = (1.6 / 1.9) * 100 = 84.21%Percentage of Fe4+ = (0.3 / 1.9) * 100 = 15.79%This calculation matches option (b). The premise of Fe4+ is unusual, but the calculation path leads to the given answer.

Answer

(a) Fe3+ = 82.98% and Fe++ = 17.02%

Answer

(b) Fe3+ = 84.21% and Fe4+ = 15.79%

Answer

(c) Fe3+ = 15.79% and Fe4+ = 84.21%

Answer

(d) Fe3+ = 17.02% and Fe++ = 82.98%

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