Answer / amruthasesh

It is because the freezer when kept at top cools the circulated air in contact with it thus making it denser than the air below. Thus cooled air comes down and the hotter air being less dense moves up. Imagine if the freezer is at the bottom..circulation will not be possible as cold air being dense will continue to remain at the bottom and hot air being light will continue to be at the top. This is nothing but natural convection phenomena.

Answer / harish saini

Due to convection current

Question 52 - The half-life for first order reaction could be described in the differential equation dC / dt = -kC where k is a constant, C is concentration and t is time. (a) Find the equation of C as a function of t. (b) Find the half life for such reaction or the time required to reduce 50 % of the initial concentration, where k = 0.139 per minute. (c) When the initial concentration Co is 16 mol / cubic metre, how long does the reaction required to achieve the final concentration of 1 mol / cubic metre?

1 Answers  

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Question 88 - In the calculation of the growth of bacteria, colony forming unit (CFU) in serial dilution is used. In a laboratory, viable count assay is used to estimate CFU. Formula applied is CFU / mL = (number of colonies x dilution) / (amount plated, in unit mL). Acceptable plate count is either between 20 and 200 or between 30 and 300 according to 2 different references. A wastewater sample of 200 ml is added to and mixed with 1.8 L of sterile water. Another 200 ml of the mixture is added to and mixed with 1.8 L of sterile water. (a) Calculate the dilution of first mixture and the dilution of the second mixture. (b) 100 microlitres of wastewater samples from the first mixture and the second mixture are placed separately on 2 different alga plates. The first plate has 250 colonies and the second plate has 23 colonies. Calculate the average CFU / mL.

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why GOD ALMIGHTY has made every living thing by water?

5 Answers  

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i want pattern of ONGC Written examination

13 Answers   IOCL, ONGC, Reliance,

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List the advantages and disadvantages of a pfr?

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Dielectric materials in static fields

0 Answers   HCL,

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What is the process of including heat exchangers in ammonia refrigeration system?

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testing formula for oxygen by ammonium chloride,ammonium hydroxide and copper

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what is the difference between distillation column and distillation tower?

3 Answers  

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