Problem 43 - Chemistry An Atoms First Approach

Question

Are the following processes exothermic or endothermic? a. When solid \(\mathrm{KBr}\) is dissolved in water, the solution gets colder. b. Natural gas \(\left(\mathrm{CH}_{4}\right)\) is burned in a furnace. c. When concentrated \(\mathrm{H}_{2} \mathrm{SO}_{4}\) is added to water, the solution gets very hot. d. Water is boiled in a teakettle.

Step-by-Step Solution

Answer

a. Endothermic b. Exothermic c. Exothermic d. Endothermic

Step 1: a. Solid KBr dissolved in water

In this process, the solution gets colder when solid KBr (potassium bromide) is dissolved in water. This indicates that heat is being absorbed from the surroundings (which is why the temperature of the solution decreases). Therefore, this process is endothermic.

Step 2: b. Natural gas burned in a furnace

When natural gas (CH4 or methane) is burned in a furnace, a combustion reaction takes place. Combustion reactions are exothermic processes, as they release heat to the surroundings. Therefore, this process (burning natural gas) is exothermic.

Step 3: c. Concentrated H2SO4 added to water

When concentrated sulfuric acid (H2SO4) is added to water, the solution gets very hot as a result of the heat generated from the reaction. Since the temperature of the solution increases because heat is released, this process is exothermic.

Step 4: d. Water boiled in a teakettle

Boiling water in a teakettle requires heat in order to change the state of water from liquid to vapor. This process absorbs heat from its surroundings, making it an endothermic process.