The drinking water standard of the World Health Organization (WHO) for arsenic i
ID: 1045246 • Letter: T
Question
The drinking water standard of the World Health Organization (WHO) for arsenic is 10.0 ?g/L. Some water from tube wells in Bangladesh was found to contain as much as 1.60 mg/L of arsenic per liter. How many times above the WHO standard is this level??
An aqueous solution known as Ringer's lactate is administered intravenously to trauma victims suffering from blood loss or severe burns. The solution contains the chloride salts of sodium, potassium, and calcium and is also 4.75 mM in sodium lactate (NaC3H5O3).? How many grams of sodium lactate are needed to prepare 12.5 liters of Ringer's lactate??
A beaker contains 1.00 x 102 grams of 0.800 M NaCl. If you transfer 50.0 grams of the solution to another beaker, what is the molarity of the solution remaining in the first beaker??
Explanation / Answer
Ans. #1. Given, WHO standard [As] = 10.0 ug L-1
Bangladesh tube well’s [As] = 1.60 mg L-1 = 1600.0 ug L-1
Now,
Times of [As] above WHO standard = Bangladesh tube well’s [As] / WHO standard [As]
= 1600.0 ug L-1 / 10.0 ug L-1
= 160
#2. Required moles of Na-lactate = Molarity x Volume of soln. in liters
= 0.00475 M x 12.5 L
= 0.059375 mol
Now,
Required mass of Na-lactate = Required moles x MW
= 0.059375 mol x (112.060668v g/ mol)
= 6.6536 g
#3. Molarity is the concentration of a solute in terms of moles per liter of solution.
Or, it’s the ratio of moles of solute to volume of solution in liters.
#Since solutions are homogenous, the removal of a fraction of the solution does not changes the moles/L ration of remaining solution.
That is, the molarity of the solution in first beaker remains unaffected of the amount of solution removed from it.
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