Analyzing Experimental Procedures and Apparatus

A research team investigated the photoelectrochemical (PEC) water-splitting efficiency of a bismuth vanadate ($BiVO_4$) photoanode. The experimental apparatus consisted of a three-electrode PEC cell connected to a potentiostat. The working electrode (photoanode) was illuminated by a simulated solar light source equipped with an Air Mass (AM) 1.5G filter and a water-filled optical filter. The electrochemical cell contained a $0.5\text{ M } Na_2SO_4$ aqueous electrolyte. A platinum ($Pt$) wire counter electrode was used to complete the circuit, and a silver/silver chloride ($Ag/AgCl$) electrode served as the reference. The gaseous products evolved at the electrodes were swept by an inert carrier gas into a gas chromatograph for quantification.

Match each component of the experimental apparatus to its primary function in this experimental setup.

A student constructs a respirometer apparatus to measure the rate of cellular respiration ($O_2$ consumption) in germinating seeds. Match each component of the apparatus to its primary experimental function in the setup.

Experiment 1

A student constructs an electrolytic cell apparatus to measure the rate of copper electroplating. As shown in the setup, a nickel cathode strip is submerged in an aqueous $1.0\text{ M } \text{CuSO}_4$ solution alongside a copper anode. Both electrodes are connected to a DC power supply and an ammeter. Before turning on the power supply, the student thoroughly washes the nickel cathode with distilled water and acetone, allows it to dry completely, and measures its mass on an analytical balance.

What is the primary procedural purpose of drying the nickel cathode completely before recording its initial mass?

A student sets up an apparatus using a reaction flask and a gas syringe to measure the volume of oxygen gas evolved during the chemical decomposition of hydrogen peroxide ($H_2O_2$) catalyzed by manganese dioxide ($MnO_2$). Based on standard laboratory procedures, place the following steps of the experimental process in the correct chronological order from first to last.

Experiment 1

A student constructed an apparatus to compare the rate of heat conduction along four metal rods (aluminum, copper, iron, and brass) of identical length and cross-sectional area. One end of each metal rod was inserted through a sealed insulated lid into a bath of boiling water maintained at $100^\circ\text{C}$. Small wooden beads were attached along the exposed outer portion of each rod at $5\text{ cm}$ intervals using a thin, uniform coating of paraffin wax. As thermal energy conducted along each rod, the wax melted, causing the beads to release and drop off into a collection tray. The student recorded the time required for the bead at the $15\text{ cm}$ mark on each rod to fall.

In Experiment 1, what was the primary procedural purpose of attaching wooden beads with paraffin wax at fixed distances along the metal rods?

A student performs an experiment to determine the specific heat capacity of an unknown solid alloy block using a water calorimeter. The apparatus includes a hot plate with a boiling water bath, an insulated calorimeter cup containing cool distilled water, a temperature probe, and a manual stirrer.

Based on standard experimental procedure, arrange the following steps in the correct chronological sequence from first to last:

Experiment 1
Students constructed a continuous-flow soil leaching apparatus to analyze solute transport through saturated soil columns under controlled hydraulic conditions.

The apparatus consists of four primary components:
1. A Vacuum Degasser Unit attached to the influent water supply line before fluid enters the soil column.
2. A Mariotte Bottle Reservoir mounted above the column to supply the influent liquid.
3. An In-Line Electrical Conductivity (EC) Sensor installed directly at the outflow port at the column base.
4. An Automated Fraction Collector positioned beneath the outflow port.

Match each component of the experimental apparatus with its primary procedural function.

Experiment 1

Students set up a capillary potometer to measure the rate of water uptake (transpiration) by a leafy plant shoot under different light intensities. The apparatus consists of a plant stem fitted tightly into a water-filled glass tube connected horizontally to a calibrated capillary tube containing a single air bubble. Attached above the capillary tube is a water reservoir controlled by a stopcock valve.

Based on the described experimental setup, which of the following best explains the purpose of including the water reservoir and stopcock valve in this apparatus?

Experiment 1
Students conducted a gravimetric analysis to determine the phosphate concentration in a water sample by precipitating magnesium ammonium phosphate hexahydrate ($\text{MgNH}_4\text{PO}_4 \cdot 6\text{H}_2\text{O}$). The apparatus included a Büchner funnel, a heavy-walled filter flask attached to a vacuum aspirator line, filter paper, a wash bottle filled with ice-cold dilute ammonia solution, and an oven.

To ensure quantitative transfer, efficient impurity removal, and accurate final mass measurement of the precipitate without losing product, in what chronological order should the students perform the following steps of the filtration and drying procedure?

Experiment 1
Students investigated the rate of carbon dioxide ($CO_2$) evolution during the reaction between calcium carbonate ($CaCO_3$) and hydrochloric acid ($HCl$). The apparatus setup consisted of several components designed to ensure accurate measurement of dry gas at a stable temperature.

Based on the described experimental setup, match each apparatus component on the left with its specific procedural function on the right.

Experiment 1
Students measured the heat of combustion of three liquid fuel samples using a bomb calorimeter apparatus. A small sample of fuel was placed in a sealed steel reaction vessel (the bomb) filled with pure oxygen. The bomb was submerged in an insulated container filled with $2,000\text{ mL}$ of distilled water. An electric ignition wire ignited the fuel. A motorized stirrer continuously agitated the surrounding water bath, while a digital thermal sensor recorded the temperature of the water every 5 seconds until a maximum temperature was observed.

What was the primary purpose of continuously operating the motorized stirrer during this experimental procedure?

Experiment 1

Students investigated the rate of enzymatic hydrolysis of $o$-nitrophenyl-$\beta$-D-galactopyranoside ($ONPG$) catalyzed by the enzyme lactase. The reaction yields $o$-nitrophenol, a product that absorbs light strongly at a wavelength of $420\text{ nm}$. To accurately measure the rate of product formation using a spectrophotometer without error from background absorbance or premature reaction, which of the following represents the correct chronological sequence of procedural steps the students must perform?

Experiment 1
Students constructed a Soxhlet extraction apparatus to isolate lipids from an algal biomass sample using an organic solvent. The apparatus consists of a boiling flask on a heating mantle, a thimble chamber containing the solid algal sample, an outer vapor tube, a side-arm siphon tube, and a water-cooled reflux condenser mounted at the top.

During operation, solvent boiled in the flask rises as vapor, condenses, and continuously washes over the solid sample inside the extraction chamber until a siphon cycle is triggered.

Match each apparatus component below with its primary procedural function in the extraction process.

Study 1
Students determined the soil organic matter (SOM) percentage of a soil sample using a loss-on-ignition (LOI) procedure. The apparatus consisted of an analytical balance, porcelain crucibles, a drying oven ($105^\circ\text{C}$), a high-temperature muffle furnace ($550^\circ\text{C}$), and a desiccator containing active silica gel desiccant.

Based on standard laboratory procedures for analyzing soil composition and controlling moisture error, in what chronological sequence should the students perform the steps below?

Experiment 1
Students set up an electrolysis apparatus to produce hydrogen gas ($H_2$) and chlorine gas ($Cl_2$) from an aqueous sodium chloride ($NaCl$) solution. The apparatus consisted of a U-shaped glass tube separated into two distinct chambers by a porous ceramic diaphragm placed at the bottom bend. Platinum electrodes connected to a direct-current power source were immersed in each chamber. Chamber 1 contained the cathode, where $H_2$ gas and hydroxide ions ($OH^-$) were generated. Chamber 2 contained the anode, where $Cl_2$ gas was generated.

Based on the described experimental setup, what is the primary procedural function of the porous ceramic diaphragm between Chamber 1 and Chamber 2?

Study 1
Students performed a column chromatography experiment to isolate chlorophyll $a$ from a spinach leaf extract using a silica gel column and a hexane-acetone solvent mixture.

Based on standard laboratory protocol for column chromatography, place the following procedural steps in the correct chronological order from first to last.

Experiment 1
Students constructed a constant-volume gas thermometry apparatus to calibrate a high-precision temperature sensor by measuring pressure changes in a gas sample across various temperatures. The experimental assembly includes a constant-volume gas bulb, a variable-temperature oil bath, a mercury manometer, and a vacuum desiccant trap.

Match each apparatus component to its primary procedural function in the experiment.

Experiment 1
Students assembled a constant-head permeameter apparatus to measure the hydraulic conductivity ($K$) of a compacted soil core. The apparatus consisted of a cylindrical soil container fitted with porous end plates to retain the soil while allowing water flow. Water was continuously supplied to an upper overflow reservoir to maintain a constant head difference ($\Delta h$) between the inlet at the top and an overflow outlet at the bottom. Two manometer tubes were tapped directly into the side of the soil container at a fixed vertical distance ($L$) apart to monitor pressure head within the soil core. Water discharging from the bottom outlet was collected in a graduated cylinder over a measured time interval ($t$).

What was the primary function of tapping the two manometer tubes directly into the sides of the soil container rather than relying on the water levels in the external upper and lower supply reservoirs?

Experiment 1
Students performed a gravimetric analysis to determine the concentration of sulfate ions ($\text{SO}_4^{2-}$) in a water sample using a precipitation and vacuum filtration apparatus.

Arrange the following experimental steps in the correct procedural order from first to last to ensure complete precipitation, crystal growth, isolation, and mass determination of the resulting barium sulfate ($\text{BaSO}_4$).

Experiment 1
Students assembled a continuous-flow photocatalytic reactor system to evaluate the degradation kinetics of an aqueous organic pollutant under ultraviolet ($\text{UV}$) light. The system consists of four primary components: a peristaltic metering pump, a quartz reaction column coated internally with titanium dioxide ($\text{TiO}_2$), a degassing bubbler module supplying compressed air, and an inline UV-Vis flow-through spectrophotometer.

Match each apparatus component used in Experiment 1 to its primary function within the experimental setup.