Question

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)

Answer 1

The approximate amount of heat absorbed by the reaction in the calorimeter is 2493.72 J, calculated using the mass of the solution, the specific heat capacity, and the change in temperature.

Step-by-step explanation:

To calculate the amount of heat absorbed by the reaction in a calorimeter, first we need to understand that the temperature decrease in the calorimeter corresponds to the heat absorbed by the reaction. Since the temperature fell by 4.3°C when 3.72 g of Ba(OH)2 · 8 H2O was added to the solution, we'll use the specific heat capacity of the solution and the mass of the solution including the added Barium hydroxide octahydrate.

The mass of the solution is 133 g of water plus the mass of the two solids: Ba(OH)2 · 8 H2O (3.72 g) and NH4SCN (1.26 g), which totals 138 g. Using the formula q = mcΔT, where q is the heat absorbed, m is the mass, c is the specific heat capacity (4.20 J/g°C), and ΔT is the change in temperature (-4.3°C), we calculate the approximate amount of heat absorbed.

Thus, the approximate amount of heat absorbed by the reaction is: q = (138 g)(4.20 J/g°C)(-4.3°C) = -2493.72 J. However, since the question is about the heat absorbed, and heat absorbed is a positive value, we disregard the negative sign and report the value as 2493.72 J.

Answer 2

The amount of heat absorbed by the reaction is 2491.92 J

Step-by-step 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