Question

Two solutions, 100.0 mL of 1.00 M AgNO3(aq) and 100.0 mL of 1.00 M NaCl(aq), both initially at 22.4 °C, are added to a Styrofoam-cup calorimeter and allowed to react. The temperature rises to 30.2 °C.

(a) Write a net ionic equation between AgNO3(aq) and NaCl(aq) indicating whether a precipitate forms.
(b) Calculate qrxn per mole of AgCl(s) in the reaction. Express qrxn to two significant figures.
(c) Is the reaction endothermic or exothermic?

Answer 1

The net ionic equation for the reaction is Ag+(aq) + Cl-(aq) → AgCl(s), indicating the formation of a precipitate. The heat of reaction (qrxn) per mole of AgCl formed is -2.9 kJ. Since heat is released and the sign of qrxn is negative, the reaction is exothermic.

Step-by-step explanation:

To address the student's question, first, we need to write the net ionic equation for the reaction between AgNO3(aq) and NaCl(aq), which is:

Ag+(aq) + Cl-(aq) → AgCl(s)

A precipitate of AgCl forms as indicated by the solid state symbol (s).

Next, to calculate the heat of reaction (qrxn) per mole of AgCl(s), we use the provided Δrxn = -2.9 × 103 J, which is the amount of heat produced. Since it's per mole and we have 1 mole of AgNO3 reacting, qrxn is the same value, that is -2.9 kJ. The reaction is exothermic, as indicated by the negative sign.