2. To spectrophotometrically determine the mass percent of cobalt in an ore containing cobalt and some inert materials, solutions with known [Co2+] are prepared and the absorbance of each of the solutions is measured at the wavelength of optimum absorbance. The data are used to create a calibration plot, shown below. Absorbance 0.90- 0.80- 0.70- 0.60- 0.50 0.40- 0.30- 0.20- 0.10- 0.00++ 0 0.005 0.0103 0.015 Concentration (M) .04. A 0.630 g sample of the ore is completely dissolved in concentrated HNO3(aq). The mixture is diluted with water to a final volume of 50.00 mL. Assume that all the cobalt in the ore sample is converted to Co²+ (aq). (a) What is the [Co2+] in the solution if the absorbance of a sample of the solution is 0.74 ? (b) Calculate the number of moles of Co²+ (aq) in the 50.00 mL solution. (c) Calculate the mass percent of Co in the 0.630 g sample of the ore.

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Chapter1: Chemical Foundations
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M
(2022-23) Unit 1: Mole Concept,
Unit 4 (FR) (Version 2) Assessment: Chemical Reactions
0.90
0.80-
0.70-
3 0.60
0.50-
0.40-
0.30-
Absorbance
2.
To spectrophotometrically determine the mass percent of cobalt in an ore containing cobalt and some inert
materials, solutions with known [Co²+] are prepared and the absorbance of each of the solutions is measured at
the wavelength of optimum absorbance. The data are used to create a calibration plot, shown below.
0.20
0.10-
0.00+
ㅏ
0.005
0.010 34 0.015
Concentration (M) .04
co₂
100-
pertoc
A 0.630 g sample of the ore is completely dissolved in concentrated HNO3(aq). The mixture is diluted with
water to a final volume of 50.00 mL. Assume that all the cobalt in the ore sample is converted to Co²+ (aq).
(a) What is the [Co²+] in the solution if the absorbance of a sample of the solution is 0.74 ?
(b) Calculate the number of moles of Co²+ (aq) in the 50.00 mL solution.
(c) Calculate the mass percent of Co in the 0.630 g sample of the ore.
Answer the following questions relating to HC1, CH₂Cl, and CH₂Br.
(a) HCl(g) can be prepared by the reaction of concentrated H₂SO (aq) with NaCl(s), as represented by the
following equation.
H₂SO4(aq) + 2 NaCl(s) → 2 HCl(g) + Na₂SO₂(aq)
(i) A student claims that the reaction is a redox reaction. Is the student correct? Justify your answer.
(ii) Calculate the mass, in grams, of NaCl(s) needed to react with excess H₂SO4(aq) to produce 3.00 g of
HCl(g). Assume that the reaction goes to completion.
H
Transcribed Image Text:M (2022-23) Unit 1: Mole Concept, Unit 4 (FR) (Version 2) Assessment: Chemical Reactions 0.90 0.80- 0.70- 3 0.60 0.50- 0.40- 0.30- Absorbance 2. To spectrophotometrically determine the mass percent of cobalt in an ore containing cobalt and some inert materials, solutions with known [Co²+] are prepared and the absorbance of each of the solutions is measured at the wavelength of optimum absorbance. The data are used to create a calibration plot, shown below. 0.20 0.10- 0.00+ ㅏ 0.005 0.010 34 0.015 Concentration (M) .04 co₂ 100- pertoc A 0.630 g sample of the ore is completely dissolved in concentrated HNO3(aq). The mixture is diluted with water to a final volume of 50.00 mL. Assume that all the cobalt in the ore sample is converted to Co²+ (aq). (a) What is the [Co²+] in the solution if the absorbance of a sample of the solution is 0.74 ? (b) Calculate the number of moles of Co²+ (aq) in the 50.00 mL solution. (c) Calculate the mass percent of Co in the 0.630 g sample of the ore. Answer the following questions relating to HC1, CH₂Cl, and CH₂Br. (a) HCl(g) can be prepared by the reaction of concentrated H₂SO (aq) with NaCl(s), as represented by the following equation. H₂SO4(aq) + 2 NaCl(s) → 2 HCl(g) + Na₂SO₂(aq) (i) A student claims that the reaction is a redox reaction. Is the student correct? Justify your answer. (ii) Calculate the mass, in grams, of NaCl(s) needed to react with excess H₂SO4(aq) to produce 3.00 g of HCl(g). Assume that the reaction goes to completion. H
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