In April 2016, the FDA proposed an action level, or limit, of 100 parts per bill
ID: 700877 • Letter: I
Question
In April 2016, the FDA proposed an action level, or limit, of 100 parts per billion (ppb) for arsenic in infant rice cereal. what is this concentration in a) ppm? b) g/g? c) mol/kg (termed molality'")? 2. (15 points) One ounce of an infant rice cereal contains sample of an infant rice cereal was analyzed and determined to have an arsenic mass of 2.7 g. Is it safe for a baby to be fed this cereal according to the limit described in Problem #1? 3. (20 pts) A wastewater treatment plant removes all the TDS content from a water with an influent concentration of 0.25 mg/L. Sample analysis shows that there are equal concentrations of KCl, CaSO4, NaHCO3. What is the molarity (M) of each compound?Explanation / Answer
Ans 1
Part a
Concentration in ppm = 100 ppb x 1ppm/1000ppb
= 0.1 ppm
Part b
Concentration in ug/g = 0.1 ppm x (1mg/kg / 1ppm)
= 0.1 mg/kg x (1kg/1000g) x (1000ug/mg)
= 0.1 ug/g
Part C
Concentration in mol/kg = 0.1 ug/g / molecular weight of arsenic
= [(0.1 ug/g) x (1g/10^6ug)] / (74.92g/mol)
= 1.3347 x 10^-9 mol/g x (1000g/1kg)
= 1.3347 x 10^-6 mol/kg
Ans 2
Concentration of arsenic in rice cereal
= mass of arsenic / mass of rice cereal
= 2.7 ug/1 ounce x (1 ounce /28.35g)
= 0.0952 ug/g
From the previous question part b
0.0952 ug/g < 0.1 ug/g
This is safe for a baby.