Answer:
the initial temperature of the iron sample is Ti = 90,36 °C
Explanation:
Assuming the calorimeter has no heat loss to the surroundings:
Q w + Q iron = 0
Also when the T stops changing means an equilibrium has been reached and therefore, in that moment, the temperature of the water is the same that the iron ( final temperature of water= final temperature of iron = T )
Assuming Q= m*c*( T- Tir)
mc*cc*(T-Tc)+mir*cir*(T - Tir) = 0
Tir = 20.3 °C + 300 g * 4.186 J/g°C * (20.3 C - 19 °C) / ( 51.9 g * 0.449 J/g°C )
Tir = 90.36 °C
Note :
- The specific heat capacity of water is assumed 1 cal/g°C = 4.186 J/g°C
- We assume no reaction between iron and water
Answer is (4) - Pb.
According to the reactivity series of elements
- the elements which are above the hydrogen are more reactive than hydrogen.
- the elements which are below the hydrogen are less reactive than hydrogen.
Among the given choices, only Pb is placed above the hydrogen in the reactivity series and rest are below the hydrogen.
Hence, Pb is more active than hydrogen.
