Question

convert ammonia into nitrate using the procedure below a researcher compared the amountsof ammonia present in the bacterial cultures of three different salt concentrations to theamount of ammonia present in a control bacteria treatment1. Set up four bacterial cultures and water.2. add different amounts of salt to three of the bacterial cultures to produce salinity levelsof 0.5%, 1.0% and 2.0%3.add the same amount of ammonia of a specific concentration to each culture.4. after four hours collect one sample from each of the bacterial cultures.5. Measure the ammonia concentration in each culture.6. repeat steps one through 5 three additional times and average the results from eachculture.At the completion of the investigation the researcher was concerned that the effect ofthe salt on the ability of the bacteria to react with ammonia was not truly measuredwhich of the following statements best describes a flaw the researcher identified?A. the ammonia of bacteria in each salt solution with ammonia should have beendecreased.B. the growth of bacteria in salt solution should have been determined before addingammonia.C. The ammonia levels in the bacterial cultures in salt solutions should have beenmeasured after less time.D. the bacterial cultures in the salt solution should have been exposed to a greaterconcentration of ammonia.

Answer 1

The correct option is B. the growth of bacteria in salt solution should have been determined before adding ammonia. The experimental desing introduced a variable (salt concentration) without testing its effect in bacterial growth (and thus ammonia intake).