Question

Initially a bottle contained 400 g of ethanol. Half of ethanol was used by a student for preparing the stock solution in an environmental chemistry laboratory just before summer vacation of 90 days. After completing the procedure, the student left the bottle uncorked. If the unsealed bottle losses ethanol at a rate of 0.5 g/day, the ethanol that will be left in the bottle at the end of the summer vacation is __________ g (an integer value).

Answer 1

Correct Answer: 155

Step 1: Calculate the remaining ethanol after initial use. \[ \text{Remaining Ethanol after Use} = 400 \, \text{g} - 200 \, \text{g} = 200 \, \text{g} \] Step 2: Determine the total ethanol loss due to evaporation over 90 days. \[ \text{Total Loss} = 0.5 \, \text{g/day} \times 90 \, \text{days} = 45 \, \text{g} \] Step 3: Calculate the ethanol left at the end of the vacation. \[ \text{Ethanol Left} = 200 \, \text{g} - 45 \, \text{g} = 155 \, \text{g} \]