A closed system is completely closed to the outside environment. Every interaction is transmitted inside that closed system.
Hrxn = Q reaction / mol of reaction
mol of reaction = M * V = 10 * 1 = 10 mmol = 0.01 mol
Q water = m * C * (Tf - Ti)
= (10 + 10) (4.184) (26-20) = 502.08 J
Q reaction = - Q water = -502.08 J
Hrxn = -502.08 / (0.01) = - 50208 J = - 50.21 kJ/mol
The results of Dominic and Eva's experiment is unreliable and can lead to a pseudoscientific claim primarily because they did not repeat their tests multiple times. Although, they used the same type of stopwatch in recording the time it takes for the chemical reaction to occur, they have different reactions times. Thus, it would have been better if they conducted several trials then obtained the average of their results.
First, we convert the given amount of energy into joules.
1 kJ = 1000 joules
2.2125 kJ = 2,212.5 Joules
Each kilocalorie contains 4,184 Joules
Kilocalories = 2,212.5 / 4,182
Kilocalories = 0.529
1 kilocalorie = 1000 calories
0.529 kilocalories = 529 calories
