Exothermic Reactions

The beaker feels warm, meaning the temperature of the surroundings (the beaker and water) has increased.

An exothermic reaction releases energy to the surroundings, causing the temperature of the surroundings to increase. This matches the observation perfectly.

In an exothermic reaction, energy flows out of the chemical system into the surroundings — the surroundings get hotter, not the reaction itself.

The correct answer states the reaction is exothermic and that energy is released to the surroundings, raising their temperature.

We need to explain why the beaker becomes warm — meaning temperature has increased in the surroundings.

The choices “The reaction is endothermic, so energy is absorbed from the surroundings, cooling them.” and “The reaction is endothermic, so the products have more energy than the reactants.” both say endothermic. Endothermic reactions cause the surroundings to get colder, not warmer. Both are eliminated.

The choice “The reaction is exothermic, so the chemical system absorbs heat from the beaker.” says 'the chemical system absorbs heat from the beaker' — this describes an endothermic process, contradicting the warm beaker observation. Eliminated.

The choice “The reaction is exothermic, so energy is released to the surroundings, raising their temperature.” is the only one that correctly identifies the reaction as exothermic and states that energy is released to the surroundings, raising their temperature.

From the question: mass $m=200$ g, initial temperature $=20.0°C$, final temperature $=35.0°C$, and specific heat capacity $c=4.18$ J g⁻¹ °C⁻¹.

$\Delta T=T_{final}-T_{initial}=35.0-20.0=15.0°C$

$q=mc\Delta T=200\times 4.18\times 15.0$

$q=200\times 4.18\times 15.0=12540\text{ J}$

The energy released is 12540 J, which matches the first option.

The formula is $q=mc\Delta T$, with $m=200$ g, $c=4.18$ J g⁻¹ °C⁻¹, and $\Delta T=35.0-20.0=15.0°C$.

2508 J would result from $200\times 4.18\times 3=2508$, using $\Delta T=3$ — this is not the correct temperature change. Eliminated.

8360 J comes from $200\times 4.18\times 10=8360$, using $\Delta T=10$ instead of the correct value of 15. Eliminated.

29260 J is far too large and does not result from any correct substitution of the given values. Eliminated.

$q=200\times 4.18\times 15.0=12540$ J is the correct calculation.