Question

the qrxn is -11,500 j when 17.6 g hcl dissolves in water. what is the enthalpy of the reaction? δh_rxn = ? kj/mol enter either a + or - sign and the magnitude.

Explanation:

Step1: Calculate moles of HCl

Molar mass of HCl is \(1.008 + 35.45 = 36.458\) g/mol.
Moles of HCl, \(n=\frac{mass}{molar\ mass}=\frac{17.6\ g}{36.458\ g/mol}\approx0.4827\ mol\).

Step2: Convert \(q_{rxn}\) to kJ

\(q_{rxn}=-11500\ J=-11.5\ kJ\) (since \(1\ kJ = 1000\ J\)).

Step3: Calculate \(\Delta H_{rxn}\)

Enthalpy of reaction, \(\Delta H_{rxn}=\frac{q_{rxn}}{n}=\frac{-11.5\ kJ}{0.4827\ mol}\approx -23.8\ kJ/mol\) (rounded appropriately).

Answer:

\(-23.8\) (or more precise calculation: \(\frac{-11500\ J}{17.6\ g}\times\frac{36.458\ g}{1\ mol}\times\frac{1\ kJ}{1000\ J}=\frac{-11500\times36.458}{17.6\times1000}\approx -23.8\) kJ/mol)