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Use concentration as a conversion factor to calculate the quatitu requested in each question below. communicate your problem-solving approach, including units and correct certianty. (SD)
1. Cow's milk contains 4.5 g of lactose per 100 mL milk. What mass of
lactose is present in 250ml (one cup) of milk?
2. A 10% W/V salt solution is used for making pickles. What mass of
salt is present in 750 mL of this solution.
3. A 250 mL measuring cup of cleaning solution contains 1.2 mol of dissolved
ammonia. What is the molar concentration of this solution?
4. Fish require a concentration of about 4.5 mg/L of dissolved oxygen
in water. what colume of water woudl contain 100 mg of oxygen?
5. What volume of concentrated, 14.6 mol/L, phosphoric acid would contain
2.00 mol of solute?
6. Hard water contains at least 120 ppm of dissolved minerals. If 2.0
L of hard water in a kettle is boiled to dryness, what mass of minerals
would be obtained? (120ppm = 120 mg /1 L)
7. What ammount of table salt is needed to prepare 12.0 L of a 5.20
mol/L solution?
8. A laboratory solution of zinc nitrate is labelled 24.0 mmol/L. what
colume of this solution would contain 0.600 mol of solute?
23 (Enrichment) Concentration of a Solution
Modren analytical chemistry uses some sophisticated tehcnology to detect incredibly small quatities of substances. Chemical analysis is approaching on part per trillion concentrations. (The SI prefixes used in this exercise include nano (n) 10^-9, pico (p) 10^-12, femto (f) 10^-15, and atto (a) 10^-18)
1. An ICP ( inductively coupled plasma technology) vaporizes a small sample which is then analyzed by a mass spectrometer. The detection limit for lead using this method is 0.05 ng/mL.
a) What is the detection limit for lead in ppb?
b) What volume of solution would contain 1.0 g of lead?
2. A laser-based microchemical analysis has a detection limit
of 9 x 10^-10 mol/L using a sample colume of 0.2 pL. How many molecules
are preasent in this sample?
3. Using a sample colume of 0.2 pL, what molar concentration of solute
corresponds to the presence of one molecule?
4. The detection limit for 2,4-dinitrophenylhydrazones using capillary
liquid chromatopraphy is 15 ag in a sample volume of 0.20 pL. convert this
limit into a concentration in ppb.
