A sample of caffeine (306.4 mg) was dissolved in 200 mL water, and 2 mL of this solution was diluted to 100 mL with the same solvent. A further dilution was performed by diluting 10 mL of this solution to 50 mL, again with water. The absorbance of this solution at 273 nm was found to be 0.313 in a 1 cm cell. Calculate the percentage purity of the sample, given that the specific absorbance of caffeine at 273 nm in water is 515.  (5 marks)

According to your textbook, which of the following were the most notable race riots during Reconstruction? 

Henry Ward Beecher: 

Which of the following drugs reduces the heart rate by inhibiting the If (funny current) in SA nodal cells, and is currently licensed for add-on therapy of stable angina and heart failure?

AS, a 54-year-old man, is diagnosed with acute kidney injury. The cause of this was attributed to interstitial nephritis. Which of the following drugs does not cause interstitial nephritis?

The principle that energy cannot be created or destroyed is known as ________.

Which of the following was a major reason cattle drives declined:

Upon the routine examination and culture of a non-sterile oral saline solution, the following contaminant was isolated.    You should now complete the following paragraph by selecting the correct answer from each dropdown.   The Gram stained bacterium shown in the image above is a [IDENTIFICATION] [IDENTIFICATION2]. This method of identification provides information on the cells [TYPE] and relies upon the staining of the bacterial [COMPONENT]. It can identify in a [LEVEL] manner. This level of identification [YES] for targeted antibiotic therapy to take place.

You are determining the activity of a novel antimicrobial agent. You have been provided with a stock solution of the new antimicrobial (50mg/mL). You are required to produce an antimicrobial solution which has a final volume of 10mL. You should now complete the following table and paragraph by selecting the correct answer from each dropdown. Tube number 1 2 3 4 5 6 Volume of antimicrobial (mL) [ANSWER1] [ANSWER2] 5.0 2.0 0.002 0.0 Concentration 6.5 mg/mL 1500 µg/mL 25mg/mL [ANSWER3] 10000 ng/mL 0   The results from the experiment performed above allow you to determine the [TEST]. This would be the [RESULT].  The [Test2] can be determined by [METHOD] and is shown by [RESULT1].

Which of the following types of antibiotics is represented by the following structure