Answer: 98.6 grams
Step-by-step explanation:

As we know that,

.................(1)
where,
q = heat absorbed or released
= mass of aluminium = 12.1 g
= mass of water = ?
= final temperature =

= temperature of aluminium =

= temperature of water =

= specific heat of aluminium =

= specific heat of water=

Now put all the given values in equation (1), we get
![-12.1* 0.900* (24.9-81.7)=-[m_2* 4.184* (24.9-23.4)]](https://img.qammunity.org/2017/formulas/chemistry/high-school/6su7uitwyg2pw7of48q3noy07u4csposd0.png)

Therefore, the mass of the water in the calorimeter is 98.6 grams