A. If 365 ppb of Cd was observed, what is its equivalent in %(w/w)? B. A sample of plastic toy was treated resulting to a 1000 mL solution. What is the concentration of As in ppm if 65 µg of As is found in the sample? C. A 250 mL stock solution of 1.5 M Pb standard was prepared. What volume (in mL) of Pb stock solution must you use to prepare 50 mL of 0.15 M Pb solution?

A. If 365 ppb of Cd was observed, what is its equivalent in %(w/w)? B. A sample of plastic toy was treated resulting to a 1000 mL solution. What is the concentration of As in ppm if 65 µg of As is found in the sample? C. A 250 mL stock solution of 1.5 M Pb standard was prepared. What volume (in mL) of Pb stock solution must you use to prepare 50 mL of 0.15 M Pb solution?

Chemistry: The Molecular Science

5th Edition

ISBN:9781285199047

Author:John W. Moore, Conrad L. Stanitski

Publisher:John W. Moore, Conrad L. Stanitski

Chapter2: Chemical Compounds

Section: Chapter Questions

Problem 143QRT: The present average concentration (mass percent) of magnesium ions in seawater is 0.13%. A chemistry...

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The present average concentration (mass percent) of magnesium ions in seawater is 0.13%. A chemistry textbook estimates that if 1.00 × 108 tons Mg were taken out of the sea each year, it would take one million years for the Mg concentration to drop to 0.12%. Do sufficient calculations to either verify or refute this statement. Assume that Earth is a sphere with a diameter of 8000 mi, 67% of which is covered by oceans to a depth of 1 mi, and that no Mg is washed back into the oceans at any time.
Many over-the-counter antacid tablets are now formulated using calcium carbonate as the active ingredient, which enables such tablets to also be used as dietary calcium supplements. As an antacid for gastric hyperacidity, calcium carbonate reacts by combining with hydrochloric acid found in the stomach, producing a solution of calcium chloride, converting the stomach acid to water, and releasing carbon dioxide gas (which the person suffering from stomach problems may feel as a “burp”). Write the unbalanced chemical equation for this process.
Physiological saline concentration—that is, the sodium chloride concentration in our bodies—is approximately 0.16 M . A saline solution fur contact lenses is prepared to match the physiological concentration. If you purchase 25 mL of contact lens saline solution, how many grams of sodium chloride have you bought?
4.64 Using the web, find information about the amount of lead in the environment during the past 50 years. Correlate what you observe with the presence or absence of tetraethyl lead in gasoline.
Magnesium nitrate and barium nitrate decompose similarly on heating and the reaction can be represented as follow: M(NO3)2 (s) --› MO (s) + 2NO2 (g) + ½O2 (g), where M = Mg or Ba (a) When Group 1 nitrates (with the exception of lithium nitrate) are strongly heated, the corresponding nitrite was formed along with a colorless gas which relights a glowing splint. (i) Write a balanced equation for the thermal decomposition of potassium nitrate. (ii) Unlike other Group 1 nitrates, lithium nitrate decomposes on heating in the same way as Group 2 nitrates. Suggest a reason for the difference in behaviour, and give an equation for its decomposition. (b) Zinc carbonate and magnesium carbonate decompose when heated to give similar products. (i) Suggest an equation for the thermal decomposition of magnesium carbonate. (ii) The radius of Zn2+ cation is 0.074 nm. Use the Data Booklet to deduce whether zinc carbonate will decompose at a higher or lower temperature than magnesium carbonate. Explain…
A fertilizer railroad car carrying 34,300 gallons of commercialaqueous ammonia (30% ammonia by mass)tips over and spills. The density of the aqueous ammoniasolution is 0.88 g>cm3. What mass of citric acid,C(OH21COOH21CH2COOH22, (which contains three acidicprotons) is required to neutralize the spill? 1 gallon = 3.785 L.
What mass of carbon dioxide is produced when 1.0 gallons of gasoline is combusted? The approximate density and composition of gasoline are 0.70 g/mL and C8H18, respectively?
A mixed with extraneous matter sample containing aluminum (Al) weighs 1.35 g. the sample a was precipitated as Al (OH)3 and ignited at 1230°C to yield a precipitate of Al2O3 weighing 255.00 mg. Calculate the mass percent of Al in the sample. given that: Molar Mass of aluminum = 27.00 g/mol and Molar Mass of Al2O3 =102.00 g/mol .
Which is correct and which is incorrect from the following sentences? Proposition True False (a) The nitrogen ions N + and oxygen O + are products of the decay of the corresponding molecules under the influence of sunlight near the earth's surface. (b) Red phosphorus is more active than white phosphorus and is therefore used in the manufacture of matches. (c) The oxidation number (a.o.) of nitrogen in all chemicals NO, NO + and NO- is +2. (d) Of the elements Al, Cl2, Na, Mg and Ca, only Na reacts with cold water to produce H2. (e) Of the two common carbon oxides, monoxide is less acidic.
A supplement was tested for iron content in a laboratory. First, a random sample of 10 tabletsweighing a total of 13.7421 g was turned into fine powder. A scoop of this powder weighing2.7544 g was then dissolved and precipitated as Fe(OH)3 which was then rinsed and ignited to aconstant weight as Fe2O3 (159.69 g/mol). The recorded constant weight of Fe2O3 is 0.2629 g.a. What is the %Fe (55.85 g/mol) content of the supplement?b. What is the iron content of the supplement reported as g FeSO4∙7H2O (277.908 g/mol)per tablet?
Natural waters often contains relatively high levels of calcium ion, Ca2+, and hydrogen carbonate ion (bicarbonate), HCO3, from the leaching of minerals into the water. When such water is used commercially or in the home, heating of the water leads to the formation of solid calcium carbonate, CaCO3, which forms a deposit ('scale') on the interior of boilers, pipes, and other plumbing fixtures. Ca(HCO3)2(aq) --> CaCO3(s) + CO2(g) + H2O(l) If a sample of well water contains 2.0 X 10-3 mg of Ca(HCO3)2 per milliliter, what mass of CaCo3 scale would 1.0ml of this water be capable of depositing?
Measurements of the exhaust gases of a hydrogen-fueled engine indicate a composition of 71.0% N2, 25.0% O2, and 3.9% H2O. At what equivalence ratio was the engine operated? in hand written