Question

The Q value of a nuclear reaction, A + b → C + d, is defined by

Q=[mA+mb]−[mC+md]
where, the masses refer to the respective nuclei. Determine from the given data the Q-value of the following reactions and state whether the reactions are exothermic or endothermic.

1H+1H→2H+2H
1 3 1 1

Answer 1

The Q value of a nuclear reaction determines if the reaction is exothermic or endothermic. Exothermic reactions release energy, indicating a negative Q value, while endothermic reactions absorb energy, indicating a positive Q value.

Step-by-step explanation:

The Q value of a nuclear reaction, such as 1H + 1H → 2H + 1H, helps us understand whether the reaction is exothermic or endothermic. Exothermic reactions release energy, characterized by a negative Q value, indicating the final products have less mass than the initial reactants. Conversely, endothermic reactions absorb energy, characterized by a positive Q value, showing that the products have a higher total mass than the reactants. To determine the Q value, we use the equation Q=[mA+mb]−[mC+md].

Using examples from chemical reactions:

• For 2H2(g) + O2(g) → 2H2O(l) + 135 kcal, this is exothermic as energy is released.
• In the case of N2(g) + O2(g) + 45 kcal → 2NO(g), this reaction is endothermic since it requires an input of energy.

This correlates with the concept in nuclear reactions where an exothermic process results in a negative Q value, while an endothermic process signifies a positive Q value.