Given below from (i) to (iv) are some food items.
(i) Boiled and mashed potato
(ii) Glucose solution
(iii) A slice of bread
(iv) Mustard oil
Which of the above will give blue-black colour when tested with iodine ?

Options

A. (i) and (ii)
B. (i) and (iii)
C. (ii) and (iii)
D. (iii) and (iv)

Answer

To determine which food items will give a blue-black color when tested with iodine, we need to identify the presence of starch in each item. Here’s a step-by-step solution:

### Step 1: Understand the Iodine Test
The iodine test is used to detect the presence of starch in food items. When iodine solution is added to a substance containing starch, it turns blue-black.

### Step 2: Analyze Each Food Item
- **(i) Boiled and mashed potato**: Potatoes are known to be rich in starch. Therefore, when iodine is added, it will turn blue-black.

- **(ii) Glucose solution**: Glucose is a simple sugar and does not contain starch. Hence, it will not change color with iodine.

- **(iii) A slice of bread**: Bread is made from flour, which contains starch. Thus, when iodine is added, it will also turn blue-black.

- **(iv) Mustard oil**: Mustard oil is a fat and does not contain starch. Therefore, it will not change color with iodine.

### Step 3: Conclusion
From the analysis:
- Boiled and mashed potato (i) will give a blue-black color with iodine.
- A slice of bread (iii) will also give a blue-black color with iodine.
- Glucose solution (ii) and mustard oil (iv) will not give a blue-black color.

### Final Answer
The food items that will give a blue-black color when tested with iodine are:
- (i) Boiled and mashed potato
- (iii) A slice of bread

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