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<u>Answer:</u> The enthalpy of the reaction is -4134.3 kJ/mol
<u>Explanation:</u>
To calculate the heat absorbed by the calorimeter, we use the equation:
where,
q = heat absorbed
m = mass of calorimeter = 1.900 kg = 1900 g (Conversion factor: 1 kg = 1000 g)
c = heat capacity of calorimeter = 3.21 J/g.K
= change in temperature = 4.542 K
Putting values in above equation, we get:
Heat released by the calorimeter will be equal to the heat absorbed by the reaction.
<u>Sign convention of heat:</u>
When heat is absorbed, the sign of heat is taken to be positive and when heat is released, the sign of heat is taken to be negative.
To calculate the number of moles, we use the equation:
Given mass of hexane = 0.580 g
Molar mass of hexane = 86.18 g/mol
Putting values in above equation, we get:
To calculate the enthalpy change of the reaction, we use the equation:
where,
q = amount of heat released = -27.7 kJ
n = number of moles of hexane= 0.0067 moles
= enthalpy change of the reaction
Putting values in above equation, we get:
Hence, the enthalpy of the reaction is -4134.3 kJ/mol
The concentration in mol L-l (M) = 0.717
<h3>Further explanation</h3>Given
12% solution of tetrahydrate magnesium chloride (MgCl₂)
Required
The concentration
Solution
Tetrahydrate magnesium chloride (MgCl₂)⇒MgCl₂.4H₂O
MW = Ar Mg+2. Ar Cl+8. Ar H + 4. Ar O
MW=24.31 + 2 x 35.45 + 8 x 1.01 + 4 x 16
MW=24.31+70.9+8.08+64
MW=167.29 g/mol
12% solution = 12 % m/v = 12 g in 100 ml solution
For 1 L solution :
The concentration in g/L = 120 g/L
Convert grams to moles :