The addition of 3.72 g of Ba (OH) 2 · 8 H2O to a solution of 1.26 g of NH4SCN in 133 g of water in a calorimeter caused the temperature to fall by 4.3°C. Assuming the specific heat of the solution and products is 4.20 J/g·°C, calculate the approximate amount of heat (in J) absorbed by the reaction, which can be represented by the following equation. Ba (OH) 2 · 8 H2O (s) + 2 NH4SCN (aq) → Ba (SCN) 2 (aq) + 2 NH3 (aq) + 10 H2O (l)

The amount of heat absorbed by the reaction is 2491.92 J

Explanation:

Step 1: The balanced equation

Ba (OH) 2 · 8 H2O (s) + 2 NH4SCN (aq) → Ba (SCN) 2 (aq) + 2 NH3 (aq) + 10 H2O (l)

Step 2: Data given

mass of Ba (OH) 2 · 8 H2O (s) = 3.72g

Molar mass of Ba (OH) 2 · 8 H2O (s) = 315.46 g/mol

mass of NH4SCN = 1.26 g

Molar mass of NH4SCN = 76.122 g/mol

mass of water = 133g

Molar mass of water = 18.02 g/mol

Temperature decreases with 4.3 °C this is an endothermic reaction

specific heat of the solution and products is 4.20 J/g·°C

Step 3: Calculate heat transfer

Q = m*c*ΔT

with m = the mass = mass of Ba (OH) 2 · 8 H2O + mass of NH4SCN + mass of water = 3.72 + 1.26 + 133 = 137.98

with c = the specific heat capacity of the solution = 4.20 J/g°C

with ΔT = The change in temperature = 4.3 °C

Q = 137.98 * 4.20 * 4.3 = 2491.92 J

The amount of heat absorbed by the reaction is 2491.92 J