Environmental Chemistry in Practice Quiz

Question 1A calibration solution starts at 72 mg/L. A 15 mL sample is diluted to 180 mL without reaction. Find the final concentration in mg/L, rounded to two decimal places.

Enter a number in mg/L.

Answers within 0.005 mg/L of the expected value are accepted.

Question 2An illustrative pollutant starts at 96 mg/L and follows first-order decay with a half-life of 6 days. Find the concentration after 24 days in mg/L, rounded to two decimal places.

Enter a number in mg/L.

Answers within 0.005 mg/L of the expected value are accepted.

Question 3Dissolved tracer travels downstream with river water. Which process accounts for its main direction of travel?

Precipitation of a solid from the solutionSorption onto the river’s suspended sedimentDiffusion toward the lowest river elevationAdvection with the stream’s moving water

Question 4A contaminant attaches to soil particles and later returns to pore water after conditions change. What happened during its attachment?

The solid held the substance until later releaseThe substance lost its chemical identity on contactThe soil converted the substance into energyThe particles stopped exchanging matter with water

Question 5Treatment removes a parent contaminant from a sample. What evidence is needed before judging the products less harmful?

The amount of energy used to run the reactionThe disappearance of the parent’s analytical signalThe speed at which the parent compound reactedThe products’ effects measured after the reaction

Question 6A sensitive instrument detects an unwanted substance in a stream. What separates this finding from evidence of harmful pollution?

The decision to give the detected substance a nameThe link between measured presence and harmful doseThe fact that the sample was collected outdoorsThe presence of a numerical reading on the instrument

Question 7Ground-level ozone rises during sunny weather even away from an emission point. Which account fits its formation?

Sunlight turns suspended mineral dust into ozoneSunlight drives reactions among gases that produce ozoneVehicle engines emit ozone that becomes visible in sunlightRain droplets release stored ozone as they evaporate

Question 8Biodegradable waste enters a lake, and dissolved oxygen declines. Which mechanism explains the change?

Microbial respiration consumes oxygen during decayThe added waste stops oxygen dissolving at the surfaceDecomposition binds oxygen inside intact waste particlesThe organic matter turns oxygen directly into nitrogen

Question 9Laboratory staff analyze repeated portions of the same river sample very precisely. Which additional question tests whether the result represents the river?

The use of matching containers for repeated portionsHow neatly the laboratory arranged the repeated resultsThe location and timing of the original collectionHow many decimal places the instrument displays

Question 10A soil report describes a metal as mobile. Which account explains how soil conditions affect its movement?

Acidic water destroys dissolved metal atoms during infiltrationHeavier atoms sink through soil faster than lighter atomsAcidity changes the chemical forms present and their bindingElements move through soils in the order of their atomic numbers

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Environmental Chemistry in Practice Quiz

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