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NEET PHYSICSEasy

At what temperature is the root mean square velocity of gaseous hydrogen molecules equal to that of oxygen molecules at 47°C?

A

20 K

B

80 K

C
  • 73 K
D

3 K

Step-by-Step Solution

The root mean square velocity (vrmsv_{rms}) of a gas is given by the formula vrms=3RTMv_{rms} = \sqrt{\frac{3RT}{M}}, where TT is the absolute temperature and MM is the molar mass. Given condition: vrms(H2)=vrms(O2)v_{rms}(H_2) = v_{rms}(O_2). Squaring both sides: 3RTH2MH2=3RTO2MO2    TH2MH2=TO2MO2\frac{3RT_{H_2}}{M_{H_2}} = \frac{3RT_{O_2}}{M_{O_2}} \implies \frac{T_{H_2}}{M_{H_2}} = \frac{T_{O_2}}{M_{O_2}}.

Data from sources:

  1. Molar mass of Hydrogen (H2H_2): 2×1.0082 g/mol2 \times 1.008 \approx 2 \text{ g/mol} .
  2. Molar mass of Oxygen (O2O_2): 2×16.00=32 g/mol2 \times 16.00 = 32 \text{ g/mol} .
  3. Temperature of Oxygen (TO2T_{O_2}): 47C47^\circ\text{C}. Converting to Kelvin: T(K)=t(C)+273.15T(K) = t(^\circ\text{C}) + 273.15. TO2=47+273=320 KT_{O_2} = 47 + 273 = 320 \text{ K} .

Calculation: TH22=32032\frac{T_{H_2}}{2} = \frac{320}{32} TH22=10\frac{T_{H_2}}{2} = 10 TH2=20 KT_{H_2} = 20 \text{ K}.

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