Skip to content

Iron-EDTA complex in… (Class 12 Chemistry SQP 2025-26, Q30)

questionbuddy.in/q/cbse-12-chemistry-2025-26-sqp-q30-iron-edta-complex-food-fortification

ChemistryCBSE Class 12 · Sample paper, session 2025-26 · 4 marks · Case-based

CBSE Class 12 Chemistry sample paper 2025-26: question 30

From the official CBSE sample question paper for 2025-26, section D, question 30, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q30 · 4 marks · Case-basedCompetency-basedCoordination Compounds

Iron-EDTA complex in food fortification

Food fortification is defined as the practice of adding vitamins and minerals to commonly consumed foods during processing to increase their nutritional value. It is a proven, safe and cost-effective strategy for improving diets and for the prevention and control of micronutrient deficiencies. A food product (such as rice, wheat flour, edible oil) that is fortified through the addition of fortificants is called a "vehicle".

In African and south Asian countries 40% of the population suffers from anaemia. Average human needs nearly 10mg of iron daily. Iron fortification may be useful in fighting iron deficiencies in humans. Reduced iron and several iron salts have been used in the past as iron fortification, however, not all are suitable for this purpose, in terms of iron absorption. Recent studies have shown that beverages containing sugar fortified with either Ferrous sulphate or Fe(III)- EDTA complex have high rate of absorption of iron.

Ferrous sulphate as well as Fe(III)- EDTA is suitable to enrich sugar, but while iron from ferrous sulphate is precipitated and poorly absorbed when fortified sugar is added to beverages such as tea, Fe(III)- EDTA reacts slowly with tea and iron is not precipitated for at least 24 hr.

Fe(III)-EDTA as iron fortification, has demonstrated so far, more advantages than that observed from other iron salts, including ferrous sulphate. But, EDTA is a chelating agent and its use in food technology to prevent oxidative damage of food has been restricted. Excessive consumption of EDTA can cause abdominal cramps, nausea, low blood pressure and damage to kidneys. According to National Institute of Health, it is unsafe to consume more than 3 g of EDTA per day or continuously for more than 5 to 7 days.

The amount of EDTA necessary for 10 mg of iron fortification, is about 60 mg. This is within the safe limits and is comparable to the usual amount added to the diet.

(source: Layrisse, M., & MartInez-Torres, C. (1977). Fe (III)-EDTA complex as iron fortification. The American Journal of Clinical Nutrition, 30(7), 1166-1174.)

Based on the information provided above, answer the following questions:

  1. I.

    Why is Fe(III)-EDTA complex stable as compared to Ferrous sulphate?

    1 mark

  2. OR

    I.

    What happens when hard water is titrated against Na2EDTA?

    1 mark
  3. II.

    You are a doctor, working in Somalia. Will you recommend iron fortified food to your patients? Support your answer with references from the passage.

    1 mark
  4. III.

    What is the denticity of the ligand in the Fe(III) EDTA complex. Name the atom(s) through which it can bind to the central metal ion.

    2 marks

  5. OR

    III.

    Write the structure of EDTA. (Refer to figure 1)

    2 marks

Figure in the paper: Figure 1: structure of the Fe(III)-EDTA complex: a central Fe atom bonded (dashed lines) to two nitrogen atoms (joined by a CH2-CH2 bridge) and four carboxylate O- groups; each nitrogen carries two CH2-COO- arms. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2025-26.

Hints

Open one hint at a time and try again before the next.

Hint 1

Think about what a chelating ligand does to complex stability.

Hint 2

For II, use the passage's numbers: 40% anaemia, 60 mg of EDTA needed versus a 3 g safe limit.

Hint 3

Count the donor atoms around Fe in Figure 1.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. I. EDTA is a hexadentate chelating ligand. It binds Fe(III) through six donor atoms, forming several five-membered chelate rings, and the chelate effect makes the complex very stable. It does not release Fe to precipitate in tea, unlike simple ferrous sulphate.

    OR: When hard water is titrated with NaEDTA, the Ca and Mg ions form stable complexes with EDTA. The volume of EDTA used gives the hardness of water.

    1 mark

  2. II. Yes (with caution). The passage says 40% of people in African countries are anaemic. Fortification is described as safe, cost-effective and proven, and Fe(III)-EDTA is well absorbed and not precipitated in tea for 24 h. The 60 mg of EDTA needed for 10 mg of iron is far below the 3 g/day safe limit. I would advise patients to stay within the recommended limits and not to take EDTA continuously for more than 5–7 days.

    (Alternative 'No': prescribe it only to patients whose tests show iron deficiency, since excess EDTA or iron can harm the kidneys and cause cramps, nausea and low BP.)

    1 mark

  3. III. (a) EDTA is hexadentate, so its denticity is 6. It binds through 2 nitrogen atoms and 4 oxygen atoms (of the carboxylate groups).

    2 marks

  4. OR (b) Structure of EDTA (ethylenediaminetetraacetate ion): . The parent acid is .

Answer: I. EDTA is a hexadentate chelating ligand, so the chelate effect makes the complex stable [OR Ca²⁺/Mg²⁺ form stable EDTA complexes, used to estimate hardness]. II. Yes, within safe limits (40% anaemia; 60 mg EDTA ≪ 3 g limit). III. (a) Denticity 6, via 2 N and 4 O atoms; (b) (⁻OOCCH₂)₂N–CH₂CH₂–N(CH₂COO⁻)₂.

Where the marks are

  • Chelation/ring formation explains stability, or EDTA complexes Ca²⁺/Mg²⁺ in hardness estimation (1 mark)
  • Justified recommendation with references from the passage (1 mark)
  • Denticity 6 (1 mark) and donor atoms 2 N + 4 O (1 mark), or correct EDTA structure (2 marks)

Revise the chapter

Practise this chapterBoard-style questions from Coordination Compounds, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2025-26: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.