Heat Capacity Ratios

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Heat-Capacity Ratios for Gases Abstract A Kundt’s tube was used to find the speed of sound in various gases at 190C, leading to the determination of the heat-capacity ratios for the gases with a 95% confidence interval. The gases used in the experiment were air, argon, carbon dioxide, helium, nitrogen, and oxygen. The average speed of sound for air was obtained to be 329 ± 17.6 m/s, argon 318 ± .325 m/s, carbon dioxide 266 ± .870 m/s, helium 999 ± 2.11 m/s, nitrogen 348 ± .253 m/s, oxygen 325 ± .130 m/s. These values are very close to the accepted values for the speed of sound in these gases as explained in the Results section. As a result of such accurate laboratory determinations most of the heat-capacity ratios have a small percent error. The exception is air, this may be due to the fact that the Kundt’s tube had residue gas from the trial preceding it and there was a mixture of air and another gas. The determined values for the heat-capacity ratio (λ) are as follows: air 1.29±.03, argon 1.659±.01, carbon dioxide 1.28±.01, helium 1.65±.01, nitrogen 1.39±.01 and oxygen 1.39±.01. Experimental Procedure The procedure had been modified as follows: Instead of having a movable piston in the Kundt’s tube, a stationary microphone was at one end of the tube and a stationary speaker at the other end. Frequencies from 300-3400 Hz were sent through the tube by the speaker and the amplitude was recorded by the microphone. This method was used opposed to setting the speaker to one frequency and moving the microphone to different lengths in order to attain the data as suggested in the textbook (Garland 8th ed., Exp. 3 pp 106-118)[1]. Results As shown in Table 1, the calculated average speed of sound is compared to the accepted values with the error determined based on a 95% confidence interval. The accepted values were taken from a website online

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