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Zorluk: OrtaRate of Reaction and Collision Theory

During the thermal decomposition of dinitrogen pentoxide, 2N2O5(g)→4NO2(g)+O2(g)2\text{N}_2\text{O}_5(g) \rightarrow 4\text{NO}_2(g) + \text{O}_2(g), the concentration of N2O5\text{N}_2\text{O}_5 decreases from 0.80 mol dm−30.80\text{ mol dm}^{-3} to 0.20 mol dm−30.20\text{ mol dm}^{-3} over a time interval of 5 minutes5\text{ minutes}. What is the average rate of decomposition of N2O5\text{N}_2\text{O}_5 in mol dm−3s−1\text{mol dm}^{-3}\text{s}^{-1}?

Cevap: 0.002 mol dm^-3 s^-1

Cevap

0.002 mol dm⁻³ s⁻¹
The average rate of decomposition of a reactant is calculated by dividing the decrease in its concentration by the elapsed time in seconds. Here, the concentration change is ΔC=0.80−0.20=0.60 mol dm−3\Delta C = 0.80 - 0.20 = 0.60\text{ mol dm}^{-3} and the time in seconds is 5×60=300 s5 \times 60 = 300\text{ s}. Thus, the rate is 0.60300=0.002 mol dm−3s−1\frac{0.60}{300} = 0.002\text{ mol dm}^{-3}\text{s}^{-1}.

Adım Adım Çözüm

1
Calculate the change in concentration of the reactant
Δ[N2O5]=0.80 mol dm−3−0.20 mol dm−3=0.60 mol dm−3\Delta [\text{N}_2\text{O}_5] = 0.80\text{ mol dm}^{-3} - 0.20\text{ mol dm}^{-3} = 0.60\text{ mol dm}^{-3}
The rate depends on the amount of reactant consumed during the reaction period.
2
Convert time from minutes to seconds
Δt=5 min×60 s/min=300 s\Delta t = 5\text{ min} \times 60\text{ s/min} = 300\text{ s}
The requested unit is per second (s−1\text{s}^{-1}), so time must be converted to standard SI units.
3
Divide the concentration change by the total time in seconds
Rate=0.60 mol dm−3300 s=0.002 mol dm−3s−1\text{Rate} = \frac{0.60\text{ mol dm}^{-3}}{300\text{ s}} = 0.002\text{ mol dm}^{-3}\text{s}^{-1}
Average rate of reaction is defined as the change in concentration per unit time.

Anahtar Kavram

Average Rate of Reaction from Concentration Change
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Rate of Reaction and Collision Theory