SI units and prefixes Transitional Reasoning Download PDF

Questions

1. 1.

   An environmental chemist analyzes an industrial wastewater discharge for trace contamination. A $250\text{ mL}$ sample of wastewater is determined to contain $1.5 \times 10^{-2}\text{ mg}$ of dissolved lead. To evaluate the discharge against regulatory thresholds defined in micrograms per liter ($\mu\text{g/L}$), what is the concentration of lead in the sample?

   • A) $0.060\text{ }\mu\text{g/L}$
   • B) $6.0\text{ }\mu\text{g/L}$
   • C) $60\text{ }\mu\text{g/L}$
   • D) $600\text{ }\mu\text{g/L}$
2. 2.

   A physical chemist uses a pulsed laser system to initiate a rapid photochemical reaction in a monomer solution. The laser source generates pulses with a peak power of 2.5 MW, each having a duration of 8.0 ps. To determine the photochemical initiation yield, the laboratory software requires the energy delivered per pulse to be reported in microjoules ($\mu\text{J}$). Which value correctly represents the energy of a single laser pulse in microjoules?

   • A) $0.020\text{ }\mu\text{J}$
   • B) $0.20\text{ }\mu\text{J}$
   • C) $2.0\text{ }\mu\text{J}$
   • D) $20\text{ }\mu\text{J}$
3. 3.

   An electrochemist studies the deposition of a catalyst layer by applying a constant direct current of $1.8\text{ mA}$ across a planar working electrode with an active surface area of $25\text{ mm}^2$. To report the operating current density in standardized electrochemical modeling software, the measurement must be converted into the coherent SI derived unit of amperes per square meter ($\text{A/m}^2$). Which value correctly represents the current density delivered to the electrode surface?

   • A) $0.072\text{ A/m}^2$
   • B) $72\text{ A/m}^2$
   • C) $720\text{ A/m}^2$
   • D) $7.2 \times 10^4\text{ A/m}^2$
4. 4.

   A gas chromatography instrument delivers helium carrier gas through a capillary column at a constant volumetric flow rate of 2.4 mL/min. To model transport phenomena in fluid dynamics software configured strictly for coherent SI units, a chemist must express this volumetric flow rate in cubic meters per second (m³/s). Which value correctly represents the carrier gas volumetric flow rate in the required SI unit?

   • A) $4.0 \times 10^{-5}$ m³/s
   • B) $4.0 \times 10^{-8}$ m³/s
   • C) $1.44 \times 10^{-4}$ m³/s
   • D) $2.4 \times 10^{-6}$ m³/s
5. 5.

   A semiconductor manufacturing process deposits a thin layer of titanium nitride on a silicon substrate at a constant rate of 0.12 nm/s. To monitor film quality, a process control system requires the total thickness deposited during a 25-minute production cycle to be logged in micrometers (µm). Which value correctly represents the thickness of the deposited layer in micrometers?

   • A) 0.0030 µm
   • B) 0.018 µm
   • C) 1.8 µm
   • D) 0.18 µm
6. 6.

   A geochemist analyzing an asteroid fragment determines that a metallic mineral inclusion has a measured density of $7.8\text{ g/cm}^3$. To simulate the gravitational differentiation of the parent body, the researcher enters this physical quantity into software that requires all parameters in coherent SI derived units ($\text{kg/m}^3$). Which value correctly expresses the density of the mineral inclusion in the required SI unit?

   • A) $7.8 \times 10^{-3}\text{ kg/m}^3$
   • B) $7.8 \times 10^3\text{ kg/m}^3$
   • C) $7.8 \times 10^{-1}\text{ kg/m}^3$
   • D) $7.8 \times 10^6\text{ kg/m}^3$
7. 7.

   In a bomb calorimetry experiment, the combustion of a benzoic acid standard releases 6.5 kJ of heat into the surrounding water reservoir. To integrate this measurement into thermodynamic simulation software configured exclusively for coherent SI base units, a researcher must convert the quantity into fundamental units of mass, length, and time. Which expression correctly represents this measured thermal energy in SI base units?

   • A) $6.5 \times 10^{-3}\text{ kg}\cdot\text{m}\cdot\text{s}^{-2}$
   • B) $6.5 \times 10^3\text{ kg}\cdot\text{m}\cdot\text{s}^{-2}$
   • C) $6.5 \times 10^3\text{ kg}\cdot\text{m}^2\cdot\text{s}^{-2}$
   • D) $6.5 \times 10^6\text{ kg}\cdot\text{m}^2\cdot\text{s}^{-2}$
8. 8.

   A physical chemistry laboratory uses ultrafast laser spectroscopy to monitor bond cleavage in real time during a photochemical decomposition. The duration of an excitation laser pulse is recorded as 450 femtoseconds (fs). To integrate this measurement into kinetic modeling software calibrated in nanoseconds (ns), a researcher must convert the pulse duration into the appropriate submultiple. Which value correctly represents the pulse duration in nanoseconds?

   • A) $4.5 \times 10^{-1}$ ns
   • B) $4.5 \times 10^{2}$ ns
   • C) $4.5 \times 10^{-7}$ ns
   • D) $4.5 \times 10^{-4}$ ns
9. 9.

   An analytical chemist designs a microfluidic channel for a continuous-flow synthesis platform. The channel has a uniform cross-sectional area of $0.25\text{ mm}^2$ and an overall length of $80\text{ cm}$. To model reactant transport in simulation software requiring coherent SI units derived from the base unit of length, the total channel volume must be expressed in cubic meters. Which value correctly represents the total internal volume of the channel in $\text{m}^3$?

   • A) $2.0 \times 10^{-4}\text{ m}^3$
   • B) $2.0 \times 10^{-5}\text{ m}^3$
   • C) $2.0 \times 10^{-7}\text{ m}^3$
   • D) $2.0 \times 10^{-10}\text{ m}^3$
10. 10.

    A pharmaceutical quality-control laboratory monitors particulate residues in an injectable formulation and detects an active residue mass of $6.4 \times 10^4\text{ }\mu\text{g}$ in a batch sample. According to protocol, the laboratory information management system requires all analytical records to be converted into the SI base unit of mass. Which expression correctly reports this measured quantity in the SI base unit?

    • A) $6.4 \times 10^{-2}\text{ g}$
    • B) $6.4 \times 10^{-5}\text{ kg}$
    • C) $6.4 \times 10^{-8}\text{ kg}$
    • D) $6.4 \times 10^{1}\text{ mg}$