Salt A and salt B were dissolved separately in 100 mL beakers of water. The water temperatures were measured and recorded as shown in the table below:
Salt A: initial water temp. 25.1°C final water temp. 30.2°C
Salt B: initial water temp. 25.1°C final water temp. 20.0°C
Which statement is a correct interpretation of these data?
A. The dissolving of only salt B was exothermic.
B. The dissolving of only salt A was endothermic.
C. The dissolving of both salt A and salt B was endothermic.
D. The dissolving of salt A was exothermic and the dissolving of salt B was endothermic.
First eliminate answer 3: temp. of salt A increased and temp. of salt B decreased. Both salts did not react the same way.
Exothermic reactions give off heat--this causes temperatures to rise.
Endothermic reactions absorb heat--this causes temperatures to fall.
The temperature of salt A increased (exothermic reaction) while the temperature of salt B decreased (endothermic reaction).