A solution is obtained by dissolving 12g of urea (mol. wt. 60) in a litre of water. Another solution is obtained by dissolving 68.4g of cane sugar (mol. wt. 342) in a litre of water at are the same temperature. The lowering of vapour pressure in the first solution is:

Explanation

To solve the problem of determining the lowering of vapor pressure in the first solution (urea solution), we will follow these steps:

### Step 1: Calculate the number of moles of urea
To find the number of moles of urea (n1), we use the formula:

\[ n_1 = \frac{\text{mass of urea}}{\text{molecular weight of urea}} = \frac{12 \, \text{g}}{60 \, \text{g/mol}} \]

Calculating this gives:

\[ n_1 = \frac{12}{60} = 0.2 \, \text{mol} \]

### Step 2: Calculate the number of moles of cane sugar
Next, we calculate the number of moles of cane sugar (n2) using the same formula:

\[ n_2 = \frac{\text{mass of cane sugar}}{\text{molecular weight of cane sugar}} = \frac{68.4 \, \text{g}}{342 \, \text{g/mol}} \]

Calculating this gives:

\[ n_2 = \frac{68.4}{342} = 0.2 \, \text{mol} \]

### Step 3: Compare the number of moles
Now we compare the number of moles of urea and cane sugar:

- Moles of urea (n1) = 0.2 mol
- Moles of cane sugar (n2) = 0.2 mol

Since both solutions have the same number of moles (0.2 mol), we can conclude that the lowering of vapor pressure in both solutions will be the same.

### Step 4: Conclusion
The lowering of vapor pressure in the first solution (urea solution) is equal to that in the second solution (cane sugar solution) because they have the same number of moles of solute.

### Final Answer
The lowering of vapor pressure in the first solution is the same as that in the second solution.

---