Analytical Chemistry

A student weighs a sample without properly calibrating the scale and measures 31.1033, 31.1030, and 31.1033 grams. What type of error does this represent?

• Random

• Gross

• Biased

• Systematic

In the analysis of 0.7011 g of an impure chloride containing sample, 0.9805 g of AgCl were precipitated. What is the percentage by mass chloride in the sample?

• 34.59 % Cl

• 22.9 % Cl

• 30.01% Cl

• 42.67% Cl

In a 0.100 M solution at 25℃ acetic acid is found to be 1.34% dissociated. Calculate the value of Ka for HOAc

The dissociation reaction is :

HOA_c +H₂O ⇋ H₃O⁺ + OA_c^-

• 1.8 x 10^-5

• 1.2 x 10^-4

• 1.6 x 10^-4

• 2.0 x 10^-5

A 0.70 M solution of hypochlorous acid, HClO, was prepared. The Ka for the acid is 3.5 × 10^-8 .

What is the percent dissociation?

• 1.3%

• 0.84%

• 0.41%

• 0.22%

Based on the given values, rank the following complex ions from most to least stable

[Cr(OH)₄]^- K_f = 8.0 x 10²⁹

[Ni(CN)₄]^2- log(K_d)= -31.3

[Co(NH₃)₆]³⁺ K_d = 2.2 x 10^-34

[Cu(CN)₄]^3- log(K_f) = 30.3

• [Cr(OH)₄]^- , [Ni(CN)₄]^2- ,[Co(NH₃)₆]^{3+ ,} [Cu(CN)₄]^3-

• [Ni(CN)₄]^2- , [Co(NH₃)₆]³⁺ , [Cr(OH)₄]^- , [Cu(CN)₄]^3-

• [Cr(OH)₄]^- , [Cu(CN)₄]^3- , [Ni(CN)₄]^2- , [Co(NH₃)₆]³⁺

• [Co(NH₃)₆]^{3+ ,} [Ni(CN)₄]^{2- ,} [Cu(CN)₄]^3- , [Cr(OH)₄]^-

Ascorbic acid (C₆H₈O₆) is a common antioxidants that protects our bodies against radicals. In the redox equation below that occurs in our stomach, which of the following pairs identifies the reducing and oxidizing agents, respectively?

C₆H₈O₆ + 2H⁺ +2NO₂^- ———-> C₆H₆O₆ + 2H₂O + 2NO

• NO₂^- and C₆H₈O₆

• H⁺ and NO₂^-

• C₆H₈O₆ and NO₂^-

• C₆H₈O₆ and H⁺

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

In any cell (galvanic or electrolytic), the electrode where oxidation occurs is the _________ and the electrode where reduction occurs is the __________

• cathode, anode

• working electrode, counter electrode

• anode, cathode

• aathode, cathode

What is the purpose of a reference electrode?

• To provide a source of stable voltage

• To complete the circuit

• To provide a source of electrons or positive charges needed by the analyte electrode

• All of the above

A loss of 0.4 mg of Zn occurs during an analysis for that element. Calculate the percent relative error due to this loss if the mass of Zn in the sample is 32 mg.

• 1.25%

• 0.5%

• 5%

• 12.5%

A 50.00-mL portion of an HCl solution required 29.71 mL of 0.01963 M Ba(OH)² to reach an end point with bromocresol green indicator. Calculate the molar concentration of the HCl.

Notes: Ratio for Acid :Base = 1:2

Molar concentration = (moles of solute)/(liters of solute)

• 0.125 M HCl

• 0.023 M HCl

• 0.612 M HCl

• 0.875 M HCl