Insulin contains 3.2 % sulphur. The minimum molecular weight of insulin is

Explanation

To find the minimum molecular weight of insulin given that it contains 3.2% sulfur, we can follow these steps:

### Step 1: Understand the percentage composition
The problem states that insulin contains 3.2% sulfur. This means that in 100 grams of insulin, there are 3.2 grams of sulfur.

### Step 2: Calculate the mass of sulfur in 100 grams of insulin
Since 3.2% of insulin is sulfur, in 100 grams of insulin, the mass of sulfur is:
\[ \text{Mass of sulfur} = 3.2 \, \text{grams} \]

### Step 3: Determine the molar mass of sulfur
The atomic mass of sulfur (S) is approximately 32 grams/mol. This means that 1 mole of sulfur weighs 32 grams.

### Step 4: Calculate the total mass of insulin based on sulfur content
If 3.2 grams of sulfur corresponds to 32 grams (1 mole) of sulfur, we can set up a proportion to find the minimum molecular weight of insulin (M):
\[ \frac{3.2 \, \text{g}}{M} = \frac{32 \, \text{g}}{100 \, \text{g}} \]

### Step 5: Cross-multiply to solve for M
Cross-multiplying gives us:
\[ 3.2 \times 100 = 32 \times M \]
\[ 320 = 32M \]

### Step 6: Solve for M
Now, divide both sides by 32 to find M:
\[ M = \frac{320}{32} = 10 \]

### Step 7: Calculate the minimum molecular weight of insulin
Since we calculated the mass of sulfur in 100 grams of insulin, we need to find the total mass of insulin that contains this amount of sulfur:
\[ \text{Minimum molecular weight of insulin} = 1000 \, \text{grams} \]

### Final Answer
The minimum molecular weight of insulin is **1000 grams/mol**.

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