Analytical practice Flashcards
Gas chromatograph is a physical method of separation based on differences in:
a. Substance density and molecular weight
b. Substance solubility or absorption between a mobile and stationary phase
c. differences in sample component vapor pressure
d. substance boiling point
b. Substance solubility or absorption between a mobile and stationary phase
the function of a sample valve is to
a. trap a constant volume of the sample and periodically injected
b. periodically reversed carrier gas flow
c. provide a means to continuously purge the system
d. alternately purging a fresh sample
a. trap a constant volume of the sample and periodically injected
retention time is the time
a. taken for a peak to elute it completely
b. Required for all sample components to elute after injection of the sample
c. needed for the first peak to appear after injection
d. taken from the maximum height of a peak to appear after the injection
d. taken from the maximum height of a peak to appear after the injection
a solution is measured to have pH of 13 at 25 degrees C. Its hydronium ion is
a. 1 x 10^-13 gr mol/l
b. 1 x 10^13 gr mol/l
c. 1 x 10^-1 gr mol/l
d. 1 x 10^1 gr mol/l
a. 1 x 10^-13 gr mol/l
To find the hydronium ion concentration (H3O+) from the pH value, we can use the equation:
pH = -log[H3O+]
Given that the pH is 13, we can rearrange the equation and solve for [H3O+]:
[H3O+] = 10^(-pH)
[H3O+] = 10^(-13)
Using a scientific calculator, we find that:
[H3O+] ≈ 1 x 10^(-13) gr mol/l
Therefore, the correct answer is option a. 1 x 10^(-13) gr mol/l.
An increased solution temperature would result in
a. an increased mV potential measured for pH unit
b. a decreased MV potential measured Ph unit
c. no appreciable effect on the measurement signal
d. an error signal generated
a. an increased mV potential measured for pH unit
the main function of the reference electrode is to
a. compensate for solution temperature changes
b. produce a varying potential with respect to the solution under tests
c. provide electrical continuity between itself and the glass electrode
d. provide a changing potential linear with solution pH
c. provide electrical continuity between itself and the glass electrode
a short circuit across the pH measuring / reference electrode terminals would result in
a. an amplifier circuit that is off scale
b. a meter reading of 0
c. a meter reading fixed at 7
d. meter reading fixed at 14
c. a meter reading fixed at 7
the substance involved in an ORP reaction will
a. gain electrons
b. lose electrons
c. gain or lose electrons
d. combining a double replacement reaction
c. gain or lose electrons
the most common source of problems in an orp measuring system is
a. the reference electrode
b. the measuring electrode
c. solution temperature effects
d. amplifier nonlinearities
b. the measuring electrode
the ORP scale is expressed in
a. MA units
b. MV units
c. PH units
d. oxidation reduction units
b. MV units
the ORP is commonly sensed using
a. a noble metal electrode with a silver silver chlorine reference electrode
b. a noble metal electrode with a hydrogen reference Electrode
c. a noble metal electrode with a ferrous reference electrode
d. identical equipment that employed for pH measurement
a. a noble metal electrode with a silver silver chlorine reference electrode
positive output values for orp measuring systems are usually obtained by
a. using gold measuring electrodes
b. using platinum measuring electrodes
c. connecting the measuring electrode to the positive instrument terminal and the reference to the negative terminal
d. connecting the measuring electrode to the negative instrument terminal and the reference to the positive terminal
d. connecting the measuring electrode to the negative instrument terminal and the reference to the positive terminal
the net electrode potential measured by the ORP electrode system is
a. a measure of oxidant concentration
b. a measure of solution reduction concentration
c. a measure of solution oxidant reduction concentration ratio
d. temperature dependent
c. a measure of solution oxidant reduction concentration ratio
the response of an orp electrode system may be checked by
a. the comparison to MV potential measured by a precise voltmeter
b. comparison to a known orp solutions as reference
c. the use of saturated buffer solutions of PH4 and PH7 at known temperatures
d. replacing electrodes that are suspected to be faulty
b. comparison to a known orp solutions as reference
the conductivity of an electrolyte is
a. dependent upon the solution pH
b. related to the mobility of hydrogen ions
c. dependent upon the concentration and mobility of all ions
d. depends upon a chemical reaction involving an exchange of electrons
c. dependent upon the concentration and mobility of all ions
The conductance of a solution is measured to be 100 uS. The cell constant of the conductivity cell is 0.1/cm. The conductivity is:
a. 100 US cm
b. 100uS/cm
c. 10uS/cm
d. 10 cm/uS
c. 10uS/cm
Conductivity (σ) = Conductance (G) / Cell Constant (K)
Given:
Conductance (G) = 100 uS (microsiemens)
Cell Constant (K) = 0.1/cm
Substituting the values into the formula, we get:
σ = 100 uS / 0.1/cm
To cancel the units, we need to convert microsiemens to siemens and centimeters to meters:
1 microsiemens (uS) = 1 x 10^-6 siemens (S)
1 cm = 0.01 meters
σ = (100 x 10^-6 S) / (0.1 / 0.01 m)
Simplifying the expression, we get:
σ = (100 x 10^-6 S) / (10 m)
σ = 10^-4 S/m
Therefore, the conductivity of the solution is 10 uS/cm.
The correct answer is c. 10 uS/cm.
Conductivity measuring systems
a. are almost never temperature compensated
b. are unaffected by solution temperature changes
c. are always automatically temperature compensated
d. should be temperature compensated where the likelihood absolution temperature variation exists
c. are always automatically temperature compensated
electrolytic conductivity is
a. the effective resistance of a solution
b. the ability of a solution to pass electric current
c. a measure of the potential developed by a chemical reaction
d. dependent upon solution temperature and the presence of water
b. the ability of a solution to pass electric current
the conductance of a solution is determined by
a. correcting the measured values with application the cell constant
b. taking the reciprocal of a potential measurement
c. measuring the solution resistance per unit length
d. reading the voltage values with an instrument
d. reading the voltage values with an instrument
for a conductivity cell of electrode face area of 10 centimeters square with a distance between electrodes of 1 centimeter the cell constant is
a. 0.1/cm
b. 10/cm
c. 0.1/cm2
d. 1/cm
a. 0.1/cm
Distance between electrodes = 1 centimeter
Electrode face area = 10 centimeters square
Cell Constant = Distance between electrodes / Electrode face area
= 1 cm / 10 cm^2
= 0.1 cm / cm^2
Therefore, the answer is c. 0.1/cm.
the following is not a factor affecting conductivity measurement
a. number of species of ions and their mobilities
b. composition and concentration of solute
c. pressure of solution under test
d. temperature of measurement
c. pressure of solution under test
the analyzer displays a conductivity of 1.0uS/cm. The measured conductance is 10uS. The cell constant is
a. 0.1
b. 1.0
c. 10
d. 100
c. 10
Cell Constant = 10uS / 1.0uS/cm
To simplify the units, we can convert cm to uS by multiplying by 10:
Cell Constant = 10uS / (1.0uS/cm * 10cm)
The units of uS cancel out, leaving us with:
Cell Constant = 10 / 1.0
Cell Constant = 10
Therefore, the answer is c. 10.
an important advantage associated with electrode less connectivity measurement is the fact that
a. it is not necessary to use ac.
b. Clean solution may be measured
c. polarization of electrode is eliminated
d. the electrodes may be installed at any angle
c. polarization of electrode is eliminated
