Question 1

The major measured contributor to serum osmolality is:

Accepted Answer

A) sodium 
B) glucose 
C) BUN 
D) protein 
A) sodium 
B) glucose 
C) BUN 
D) protein A

Question 2

Osmometers utilizing the freezing point colligative property of solutions are based on what principle?

Accepted Answer

A) 1 osmole of nonionizing substance dissolved in 1 kilogram of water raises the freezing point 1.86°C. 
B) 1 osmole of nonionizing substance dissolved in 1 kilogram of water lowers the freezing point 1.86°C. 
C) Increased solute concentration will raise the freezing point of water in direct proportion to a NaCl standard. 
D) Deceased solution concentration will lower the freezing point of water in direct proportion to a NaCl standard. 
A) 1 osmole of nonionizing substance dissolved in 1 kilogram of water raises the freezing point 1.86°C. 
B) 1 osmole of nonionizing substance dissolved in 1 kilogram of water lowers the freezing point 1.86°C. 
C) Increased solute concentration will raise the freezing point of water in direct proportion to a NaCl standard. 
D) Deceased solution concentration will lower the freezing point of water in direct proportion to a NaCl standard. B

Question 3

The two methods used in the clinical laboratory to determine osmolality are:

Accepted Answer

A) osmotic pressure and boiling point 
B) boiling point and freezing point 
C) vapor pressure and osmotic pressure 
D) freezing point and vapor pressure 
A) osmotic pressure and boiling point 
B) boiling point and freezing point 
C) vapor pressure and osmotic pressure 
D) freezing point and vapor pressure D

Question 4

Suppose a lab measured serum osmolality on the same patient sample by freezing-point and vapor-pressure methods, and the osmolality measurement by the freezing-point method was found to be greater than the osmolality measurement by the vapor-pressure method.Which of the following is the most likely explanation for this discrepancy?

Accepted Answer

A) The difference in the two methods will always result in significantly different osmolalities. 
B) overhydration of the patient 
C) technologist error 
D) the presence of unexpected volatile solutes in the patient sample 
A) The difference in the two methods will always result in significantly different osmolalities. 
B) overhydration of the patient 
C) technologist error 
D) the presence of unexpected volatile solutes in the patient sample

Question 5

In the equation to estimate osmolality by calculation, why are glucose and BUN divided by 18 and 2.8, respectively?

Accepted Answer

A) to provide an estimate of the contribution of glucose and BUN to the total number of particles of each 
B) to convert each from mg/L to mmol/L 
C) to account for the number of charges on each molecule 
D) both a and b 
A) to provide an estimate of the contribution of glucose and BUN to the total number of particles of each 
B) to convert each from mg/L to mmol/L 
C) to account for the number of charges on each molecule 
D) both a and b

Question 6

In the equation to estimate osmolality by calculation, why is the sodium multiplied by two?

Accepted Answer

A) Sodium is present in body fluids in twice the concentration of other ions. 
B) Sodium has a valence of two. 
C) The equation accounts for sodium and its corresponding anion. 
D) This factor accounts for the fact that sodium may be bound to chloride (NaCl) or to bicarbonate (NaHCO3). 
A) Sodium is present in body fluids in twice the concentration of other ions. 
B) Sodium has a valence of two. 
C) The equation accounts for sodium and its corresponding anion. 
D) This factor accounts for the fact that sodium may be bound to chloride (NaCl) or to bicarbonate (NaHCO3).

Question 7

All of the following variables are needed to calculate a stool osmolal gap except:

Accepted Answer

A) stool glucose level 
B) stool sodium level 
C) stool potassium level 
D) measured stool osmolality 
A) stool glucose level 
B) stool sodium level 
C) stool potassium level 
D) measured stool osmolality

Question 8

Determine the calculated osmolality, given the following data: sodium = 140 mEq/L; glucose = 32 mmol/L; BUN = 30 mmol/L.

Accepted Answer

A) 202 mOsm/kg 
B) 292 mOsm/kg 
C) 342 mOsm/kg 
D) 404 mOsm/kg 
A) 202 mOsm/kg 
B) 292 mOsm/kg 
C) 342 mOsm/kg 
D) 404 mOsm/kg

Question 9

As the osmolality of a sample increases, the osmotic pressure ______, the boiling point _____, the freezing point ______, and the vapor pressure ______.

Accepted Answer

A) increases, increases, decreases, decreases 
B) increases, decreases, increases, decreases 
C) decreases, increases, decreases, increases 
D) decreases, decreases, increases, increases 
A) increases, increases, decreases, decreases 
B) increases, decreases, increases, decreases 
C) decreases, increases, decreases, increases 
D) decreases, decreases, increases, increases

Question 10

What is the purpose for calculating an osmolal gap?

Accepted Answer

A) This serves as a quality-control measure of osmolality measurement. 
B) This serves as an indication of abnormal concentrations of unmeasured substances in the blood stream. 
C) This is the method utilized to calibrate the osmometer. 
D) This removes the need for direct measurement of osmolality. 
A) This serves as a quality-control measure of osmolality measurement. 
B) This serves as an indication of abnormal concentrations of unmeasured substances in the blood stream. 
C) This is the method utilized to calibrate the osmometer. 
D) This removes the need for direct measurement of osmolality.

Question 11

Osmometers utilizing the vapor-pressure colligative property of solutions are based on what principle?

Accepted Answer

A) An increase in the concentration of dissolved solutes decreases the vapor pressure generated because of a lack of volatility of the typical solutes. 
B) An increase in the concentration of dissolved solutes increases the vapor pressure generated because of a lack of volatility of the typical solutes. 
C) An increase in the concentration of dissolved solutes decreases the vapor pressure generated because of an increased volatility of the typical solutes. 
D) An increase in the concentration of dissolved solutes increases the vapor pressure generated because of an increased volatility of the typical solutes. 
A) An increase in the concentration of dissolved solutes decreases the vapor pressure generated because of a lack of volatility of the typical solutes. 
B) An increase in the concentration of dissolved solutes increases the vapor pressure generated because of a lack of volatility of the typical solutes. 
C) An increase in the concentration of dissolved solutes decreases the vapor pressure generated because of an increased volatility of the typical solutes. 
D) An increase in the concentration of dissolved solutes increases the vapor pressure generated because of an increased volatility of the typical solutes.

Question 12

Calculate the osmolal gap, given the following data: measured osmolality = 366 mOsm/kg; sodium = 144 mEq/L; glucose = 5.0 mmol/L; BUN = 9.0 mg/dL.

Accepted Answer

A) 64 mOsm/kg 
B) 70 mOsm/kg 
C) 74 mOsm/kg 
D) 208 mOsm/kg 
A) 64 mOsm/kg 
B) 70 mOsm/kg 
C) 74 mOsm/kg 
D) 208 mOsm/kg

Question 13

Determine the calculated osmolality given the following data: sodium = 135 mEq/L; glucose = 95 mg/dL; BUN = 10 mg/dL.

Accepted Answer

A) 240 mOsm/kg 
B) 279 mOsm/kg 
C) 375 mOsm/kg 
D) 480 mOsm/kg 
A) 240 mOsm/kg 
B) 279 mOsm/kg 
C) 375 mOsm/kg 
D) 480 mOsm/kg

Question 14

Osmolality measurements depend on:

Accepted Answer

A) the molecular weight of particles in solution 
B) the kind of particles in solution 
C) the number of particles in solution 
D) all of the above 
A) the molecular weight of particles in solution 
B) the kind of particles in solution 
C) the number of particles in solution 
D) all of the above

Question 15

Which of the following anticoagulants will contribute the least to plasma osmolality?

Accepted Answer

A) indoacetic acid 
B) sodium fluoride-potassium oxalate 
C) heparin 
D) EDTA 
A) indoacetic acid 
B) sodium fluoride-potassium oxalate 
C) heparin 
D) EDTA

Question 16

The major clinical use for measuring urine osmolality is to evaluate ______, and the major clinical use for measuring colloid osmotic pressure is to detect conditions leading to ______.

Accepted Answer

A) the kidney's ability to dilute the urine, the kidney's ability to concentrate the urine 
B) the kidney's ability to dilute the urine, pulmonary edema 
C) the kidney's ability to concentrate the urine, the kidney's ability to dilute the urine 
D) the kidney's ability to concentrate the urine, pulmonary edema 
A) the kidney's ability to dilute the urine, the kidney's ability to concentrate the urine 
B) the kidney's ability to dilute the urine, pulmonary edema 
C) the kidney's ability to concentrate the urine, the kidney's ability to dilute the urine 
D) the kidney's ability to concentrate the urine, pulmonary edema

Question 17

Given that a normal albumin is approximately 40 g/L, a normal glucose is approximately 900 mg/L, and a normal BUN is approximately 100 mg/L, why is albumin (which has a much higher concentration) not considered in the equation to estimate osmolality?

Accepted Answer

A) Albumin concentration is so much higher than other components of the blood stream, its effect on osmolality is considered constant and thus not included in the calculation. 
B) When considering the molecular weight of albumin, the high concentration becomes a very small number of moles, causing albumin not to be included in the calculation. 
C) Albumin controls the movement of fluids in the body and does not influence osmolality. 
D) Albumin is a transport protein in the blood stream, and osmolality is only influenced by components that are being transported by albumin, not albumin itself. 
A) Albumin concentration is so much higher than other components of the blood stream, its effect on osmolality is considered constant and thus not included in the calculation. 
B) When considering the molecular weight of albumin, the high concentration becomes a very small number of moles, causing albumin not to be included in the calculation. 
C) Albumin controls the movement of fluids in the body and does not influence osmolality. 
D) Albumin is a transport protein in the blood stream, and osmolality is only influenced by components that are being transported by albumin, not albumin itself.

Exam 11: Measurement of Colligative Properties

The major measured contributor to serum osmolality is:

Osmometers utilizing the freezing point colligative property of solutions are based on what principle?

The two methods used in the clinical laboratory to determine osmolality are:

In the equation to estimate osmolality by calculation, why are glucose and BUN divided by 18 and 2.8, respectively?

In the equation to estimate osmolality by calculation, why is the sodium multiplied by two?

All of the following variables are needed to calculate a stool osmolal gap except:

Determine the calculated osmolality, given the following data: sodium = 140 mEq/L; glucose = 32 mmol/L; BUN = 30 mmol/L.

As the osmolality of a sample increases, the osmotic pressure ______, the boiling point _____, the freezing point ______, and the vapor pressure ______.

What is the purpose for calculating an osmolal gap?

Osmometers utilizing the vapor-pressure colligative property of solutions are based on what principle?

Calculate the osmolal gap, given the following data: measured osmolality = 366 mOsm/kg; sodium = 144 mEq/L; glucose = 5.0 mmol/L; BUN = 9.0 mg/dL.

Determine the calculated osmolality given the following data: sodium = 135 mEq/L; glucose = 95 mg/dL; BUN = 10 mg/dL.

Osmolality measurements depend on:

Which of the following anticoagulants will contribute the least to plasma osmolality?

The major clinical use for measuring urine osmolality is to evaluate ______, and the major clinical use for measuring colloid osmotic pressure is to detect conditions leading to ______.

Given that a normal albumin is approximately 40 g/L, a normal glucose is approximately 900 mg/L, and a normal BUN is approximately 100 mg/L, why is albumin (which has a much higher concentration) not considered in the equation to estimate osmolality?

Basic Laboratory Principles and Techniques

Spectral Techniques

Chromatography and Mass Spectrometry: Theory, Practice, and Instrumentation

Chromatographic Techniques

Laboratory Analysis of Hemoglobin Variants

Electrophoresis

Immunological Reactions

Immunochemical Techniques

Principles for Competitive-Binding Assays

Laboratory Approaches to Serology Testing

Electrochemistry: Principles and Measurement

Molecular Diagnostics

Therapeutic Drug Monitoring

Clinical Enzymology

Protein Isoforms: Isoenzymes and Isoforms

Interferences in Chemical Analysis

Sources and Control of Preanalytical Variation

Laboratory Management

Laboratory Automation

Point-Of-Care Near-Patient Testing

Laboratory Information Systems

Laboratory Statistics

Reference Intervals and Clinical Decision Limits

Quality Control for the Clinical Chemistry Laboratory

Evaluation of Methods

Classification and Description of Proteins, Lipids, and Carbohydrates

Physiology and Pathophysiology of Body Water and Electrolytes

Acid-Base Control and Acid-Base Disorders

Renal Function

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Diagnosis of Viral Hepatitis

Bone Disease

The Pancreas: Function and Chemical Pathology

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Filters

As the osmolality of a sample increases, the osmotic pressure ____, the boiling point _, the freezing point , and the vapor pressure __.

The major clinical use for measuring urine osmolality is to evaluate , and the major clinical use for measuring colloid osmotic pressure is to detect conditions leading to .