Answer : The final equilibrium temperature of the water and iron is, 537.12 K
Explanation :
In this problem we assumed that heat given by the hot body is equal to the heat taken by the cold body.


where,
 = specific heat of iron =  560 J/(kg.K)
 = specific heat of water = 4186 J/(kg.K)
 = mass of iron = 825 g
 = mass of water = 40 g
 = final temperature of water and iron = ?
 = initial temperature of iron = 
 = initial temperature of water = 
Now put all the given values in the above formula, we get:


Therefore, the final equilibrium temperature of the water and iron is, 537.12 K
 
        
             
        
        
        
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Answer: 4.1 g of barium precipitated.
Explanation:
According to avogadro's law, 1 mole of every substance occupies 22.4 L at STP and contains avogadro's number 
 of particles.
To calculate the moles, we use the equation:
Given : moles of barium = 0.030 
Molar mass of barium = 137 g/mol
x= 4.1 g
Thus there are 4.1 g of barium that precipitated.