Eval Exam Gen Chem

75問 • 3ヶ月前

問題一覧

How many significant figures are in the value of the universal gas constant R = 0.0821 L·atm·mol⁻¹·K⁻¹?

Infinite

How many significant figures should be reported in the final answer to the calculation below, assuming all given values are experimentally determined? (12.501 × 3.52 + 6.044) / 0.0042

A scientist records a temperature of 95°F. What is this temperature in Kelvin?

308.15 K

Which of the following pairs consists entirely of intensive properties?

Molarity and viscosity

Which of the following is NOT a compound?

Ozone (O3)

Which of the following statements is NOT correct about atoms?

All atoms of a given element contain the same number of neutrons.

Brass is an alloy of which two elements?

Copper and zinc (Cu and Zn)

Which of the following is NOT a chemical change?

Dissolving table salt in water

A cylinder containing a gas is compressed to half its original volume at constant temperature. What happens to its pressure?

Doubled

A 0.239 g sample of an unknown gas is placed in a 100.0 mL flask at 14°C and 600 mmHg. Which gas is it?

Chlorine (Cl2)

What is the density of propane (C3H8) at 25°C and 740 mm Hg?

1.75 g/L

Which element is the major component in solar cells?

Si (silicon)

Which family of elements has solid, liquid and gaseous members at 25°C and 1 atm?

Halogens (F to I)

What is the correct formula for ammonium hydrogen phosphate?

(NH4)2HPO4

Which of the following species does not have the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ (the argon configuration)?

Kr (krypton)

Which of the following elements has a greater electron affinity than oxygen?

Fluorine

What general trend is observed as you move from left to right across a period in the periodic table?

Atomic radius decreases

As one moves from the top to the bottom of a group in the periodic table, which of the following trends is observed?

Electronegativity decreases

Which statement correctly describes the radii of atoms and their corresponding ions?

Cations are smaller than their atoms; anions are larger than their atoms

What is the process of breaking down a large nucleus into smaller nuclei called?

Nuclear fission

Which of the following correctly describes how temperature generally affects the solubility of a solid solute in water?

Solubility increases as temperature increases.

How does increasing temperature affect the viscosity of a liquid?

Molecules move more freely, decreasing viscosity.

How many grams of potassium dichromate (K2Cr2O7, molar mass = 294.2 g·mol⁻¹) are required to prepare 250.0 mL of a 0.100 M solution?

7.36 g

An exact amount of 0.8214 g of KMnO4 (molar mass = 158.0 g·mol⁻¹) was dissolved in water and made up to volume in a 500.0-mL volumetric flask. A 200.0-mL portion of this solution was transferred to a 1000.0-mL flask and diluted to volume. Then 10.00 mL of the diluted solution was transferred to a 250.0-mL flask and diluted to volume. What is the molar concentration of the final solution?

8.32×10⁻⁵ M

Under the Brønsted–Lowry concept of acids and bases, a base is a:

Proton acceptor

Which of the following statements about pH is NOT true?

It remains constant regardless of changes in temperature.

When ammonium chloride (NH4Cl) dissolves and ionizes in water, the resulting solution will have a pH that is:

Less than 7 (<7)

In which of the following titrations does pH = 7.0 occur at the equivalence point? I. Strong acid with strong base II. Weak acid with strong base III. Strong acid with weak base

I only (strong acid and strong base)

Which of these conjugate acid–base pairs is most appropriate to prepare a buffer with pH near 7.15?

Sodium dihydrogen phosphate and sodium hydrogen phosphate (pKa2 ≈ 7.20)

What is the percent yield if 0.85 g of acetylsalicylic acid (aspirin) is obtained from the reaction of 1.00 g of salicylic acid (MW = 138 g·mol⁻¹) with excess acetic anhydride? (MW aspirin ≈ 180 g·mol⁻¹)

65%

Which piece of laboratory apparatus is NOT used for the purpose listed? Aspirator — Measure height Buret — Measure volume Calorimeter — Measure thermal energy change Desiccator — Store samples

Aspirator

Which of the following should be done before using an analytical balance?

All of the above (clean the balance and remove any sample residue; determine the sensitivity using a calibration weight; check the level of the balance by adjusting the air bubble)

Which of the following statements is correct? A. Solid reactants can be weighed directly on the pan of an analytical balance B. The weight of a liquid is approximately equal to its density C. Solid reactants can be transferred to a reaction flask using a metal spatula D. Volatile liquids can be weighed by first recording the mass of the capped empty vial

Volatile liquids can be weighed by first recording the mass of the capped empty vial

Which would be most suitable for measuring 2.7 mL of ethanol for addition to a reaction with acidified dichromate?

10-mL graduated cylinder

What is the reading of the buret shown? Options: 30.20 mL, 30.25 mL, 30.30 mL, 31.75 mL

30.30 mL

When a liquid is delivered from a volumetric pipet a small amount is typically retained in the tip. How should a student proceed to deliver the volume of liquid stated on the pipet?

Leave the small amount in the tip.

What is the correct procedure for dispensing liquids using a volumetric pipet?

Use a pipet bulb to draw liquid above the calibration mark, adjust the meniscus to the mark, then allow the pipet to drain into the receiving vessel (do not blow out unless the pipet is marked 'blow-out').

When equal volumes of the following pairs of liquids are mixed thoroughly and allowed to stand, which pair is most likely to separate into two layers?

Carbon tetrachloride and methanol

Cyclohexane and water can be separated by using a separatory funnel. Which property contributes to this separation?

Cyclohexane and water are immiscible.

When selecting a solvent for purifying a material by crystallization, which of the following is NOT a consideration?

Vapor pressure

When selecting a solvent for purifying a material by crystallization, which of the following is NOT a consideration?

Vapor pressure

What is the key step in the recrystallization process?

Allowing the hot solution to cool slowly and letting crystals grow

Which of the following factors does NOT affect the boiling point of a substance?

Mass of the substance

A round-bottom flask, a condenser, a heat source, and clamps are typically assembled in the lab for which of the following procedures?

Reflux

What is the proper way to dispose of a two milliliter sample of hexane after completing experiments with it?

Place it in a waste bottle with compatible organic materials

A student is cleaning a buret in preparation for a titration in which the buret will be filled with 0.100 M NaOH. What should be used for the final rinse of the buret?

0.100 M NaOH (the titrant solution)

Concentrated hydrochloric acid is 12.0 M and has a density of 1.18 g/mL. What is the weight percent (w/w%) of HCl? (Molar mass HCl = 36.45 g/mol)

≈ 37.1% (w/w)

A standard solution of barium hydroxide is 0.250 M. What volume of 0.200 M nitric acid is required to neutralize 10.0 mL of the barium hydroxide solution? (Reaction: Ba(OH)2 + 2 HNO3 → Ba(NO3)2 + 2 H2O)

25.0 mL

A solution is prepared by dissolving 10.00 g of a salt in 90.00 g of water. What additional information is required to calculate the molarity of the solution?

Both I and II (I: Molar mass of the salt; II: Density of the solution)

An analyst discovers that the analytical balance used in a test was improperly calibrated. What type of error does this represent?

Systematic error

An analyst repeatedly weighs a sample on an analytical balance. Each time, the reading varies slightly (0.1221 g, 0.1224 g, 0.1220 g), even though no changes are made to the sample or conditions. What is the most likely cause of this variation?

Random error due to environmental fluctuations

While performing a titration to determine the concentration of an acid, a student knocks over the buret stand partway through the experiment. Some of the titrant spills. What type of error has occurred?

Gross error due to clumsy behavior and poor lab practice

A chemist is analyzing caffeine in energy drinks using HPLC. A calibration curve is prepared by using known concentrations of pure caffeine dissolved in water. The curve is then used to determine the caffeine concentration in the drink sample. What type of quantification method is being used?

External standard

Which graph shows an instrument's response plotted against standard solution concentrations?

Calibration curve

In an electrochemical cell, the anode is a strip of magnesium. Which of the following metals is most likely to be the cathode?

Copper

Which of the following processes does NOT involve an electrochemical cell?

Heating a solution to speed up a reaction

What is the main function of the glass membrane in a pH electrode?

Responds selectively to hydrogen ion (H+) concentration

Which reagent is used in classical gas analysis to absorb oxygen quantitatively?

Pyrogallic acid (pyrogallol)

In thin-layer chromatography (TLC), the relative adsorption of the components in a mixture is expressed in terms of:

Retardation factor (Rf)

The chromatographic (TLC) plate is typically made of:

Glass

In chromatography, the relative solubility of a solute in both the stationary and mobile phases determines the:

Rate of movement of the solute

The elution power (strength) of a solvent in chromatography is primarily determined by its:

Overall polarity

In column chromatography (normal phase, polar stationary phase), the components of a sample are typically eluted in the order of:

Increasing polarity and increasing distribution ratio

Which of the following cannot be used as an adsorbent in column chromatography?

Potassium permanganate

Benzene has a smaller distribution ratio (D = concentration in stationary phase / concentration in mobile phase) in squalene than cyclohexane. Squalene is an aliphatic (nonpolar) stationary phase. Based on this, what is the order of elution of benzene and cyclohexane in GC?

Benzene will be eluted first

An environmental chemist is analyzing air samples to detect low concentrations of pollutant gases. Which of the following techniques would be most appropriate for this type of analysis?

Gas-Solid Chromatography

Ion exchange chromatography is used for all of the following applications, except:

Separation of sugars

Which of the following is not a typical application of a colorimeter?

Identifying chemical composition

A hollow cathode tube lamp is necessary in Atomic Absorption Spectroscopy (AAS) because:

Atom's absorption band is narrow.

Which of the following is an application of molecular spectroscopy?

All of the given answers

Which of the following statements about molecular spectra is correct?

All of the given choices

What is the typical wavelength range of UV radiation in the electromagnetic spectrum?

100 nm to 400 nm

Which of the following is NOT a characteristic of chromophores?

They absorb strongly at 800 nm.

Which compound is most likely to exhibit a strong IR absorption near 1700 cm⁻¹ due to a C=O stretch?

Acetone

Which technique will be most effective at distinguishing between pure samples of isotopic variants?

Mass spectrometry

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Eval Exam Lab and Org

Liane · 74問 · 3ヶ月前

Eval Exam Lab and Org

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問題一覧

How many significant figures are in the value of the universal gas constant R = 0.0821 L·atm·mol⁻¹·K⁻¹?

Infinite

How many significant figures should be reported in the final answer to the calculation below, assuming all given values are experimentally determined? (12.501 × 3.52 + 6.044) / 0.0042

A scientist records a temperature of 95°F. What is this temperature in Kelvin?

308.15 K

Which of the following pairs consists entirely of intensive properties?

Molarity and viscosity

Which of the following is NOT a compound?

Ozone (O3)

Which of the following statements is NOT correct about atoms?

All atoms of a given element contain the same number of neutrons.

Brass is an alloy of which two elements?

Copper and zinc (Cu and Zn)

Which of the following is NOT a chemical change?

Dissolving table salt in water

A cylinder containing a gas is compressed to half its original volume at constant temperature. What happens to its pressure?

Doubled

A 0.239 g sample of an unknown gas is placed in a 100.0 mL flask at 14°C and 600 mmHg. Which gas is it?

Chlorine (Cl2)

What is the density of propane (C3H8) at 25°C and 740 mm Hg?

1.75 g/L

Which element is the major component in solar cells?

Si (silicon)

Which family of elements has solid, liquid and gaseous members at 25°C and 1 atm?

Halogens (F to I)

What is the correct formula for ammonium hydrogen phosphate?

(NH4)2HPO4

Which of the following species does not have the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ (the argon configuration)?

Kr (krypton)

Which of the following elements has a greater electron affinity than oxygen?

Fluorine

What general trend is observed as you move from left to right across a period in the periodic table?

Atomic radius decreases

As one moves from the top to the bottom of a group in the periodic table, which of the following trends is observed?

Electronegativity decreases

Which statement correctly describes the radii of atoms and their corresponding ions?

Cations are smaller than their atoms; anions are larger than their atoms

What is the process of breaking down a large nucleus into smaller nuclei called?

Nuclear fission

Which of the following correctly describes how temperature generally affects the solubility of a solid solute in water?

Solubility increases as temperature increases.

How does increasing temperature affect the viscosity of a liquid?

Molecules move more freely, decreasing viscosity.

How many grams of potassium dichromate (K2Cr2O7, molar mass = 294.2 g·mol⁻¹) are required to prepare 250.0 mL of a 0.100 M solution?

7.36 g

8.32×10⁻⁵ M

Under the Brønsted–Lowry concept of acids and bases, a base is a:

Proton acceptor

Which of the following statements about pH is NOT true?

It remains constant regardless of changes in temperature.

When ammonium chloride (NH4Cl) dissolves and ionizes in water, the resulting solution will have a pH that is:

Less than 7 (<7)

In which of the following titrations does pH = 7.0 occur at the equivalence point? I. Strong acid with strong base II. Weak acid with strong base III. Strong acid with weak base

I only (strong acid and strong base)

Which of these conjugate acid–base pairs is most appropriate to prepare a buffer with pH near 7.15?

Sodium dihydrogen phosphate and sodium hydrogen phosphate (pKa2 ≈ 7.20)

65%

Aspirator

Which of the following should be done before using an analytical balance?

All of the above (clean the balance and remove any sample residue; determine the sensitivity using a calibration weight; check the level of the balance by adjusting the air bubble)

Volatile liquids can be weighed by first recording the mass of the capped empty vial

Which would be most suitable for measuring 2.7 mL of ethanol for addition to a reaction with acidified dichromate?

10-mL graduated cylinder

What is the reading of the buret shown? Options: 30.20 mL, 30.25 mL, 30.30 mL, 31.75 mL

30.30 mL

When a liquid is delivered from a volumetric pipet a small amount is typically retained in the tip. How should a student proceed to deliver the volume of liquid stated on the pipet?

Leave the small amount in the tip.

What is the correct procedure for dispensing liquids using a volumetric pipet?

When equal volumes of the following pairs of liquids are mixed thoroughly and allowed to stand, which pair is most likely to separate into two layers?

Carbon tetrachloride and methanol

Cyclohexane and water can be separated by using a separatory funnel. Which property contributes to this separation?

Cyclohexane and water are immiscible.

When selecting a solvent for purifying a material by crystallization, which of the following is NOT a consideration?

Vapor pressure

When selecting a solvent for purifying a material by crystallization, which of the following is NOT a consideration?

Vapor pressure

What is the key step in the recrystallization process?

Allowing the hot solution to cool slowly and letting crystals grow

Which of the following factors does NOT affect the boiling point of a substance?

Mass of the substance

A round-bottom flask, a condenser, a heat source, and clamps are typically assembled in the lab for which of the following procedures?

Reflux

What is the proper way to dispose of a two milliliter sample of hexane after completing experiments with it?

Place it in a waste bottle with compatible organic materials

A student is cleaning a buret in preparation for a titration in which the buret will be filled with 0.100 M NaOH. What should be used for the final rinse of the buret?

0.100 M NaOH (the titrant solution)

Concentrated hydrochloric acid is 12.0 M and has a density of 1.18 g/mL. What is the weight percent (w/w%) of HCl? (Molar mass HCl = 36.45 g/mol)

≈ 37.1% (w/w)

25.0 mL

A solution is prepared by dissolving 10.00 g of a salt in 90.00 g of water. What additional information is required to calculate the molarity of the solution?

Both I and II (I: Molar mass of the salt; II: Density of the solution)

An analyst discovers that the analytical balance used in a test was improperly calibrated. What type of error does this represent?

Systematic error

Random error due to environmental fluctuations

Gross error due to clumsy behavior and poor lab practice

External standard

Which graph shows an instrument's response plotted against standard solution concentrations?

Calibration curve

In an electrochemical cell, the anode is a strip of magnesium. Which of the following metals is most likely to be the cathode?

Copper

Which of the following processes does NOT involve an electrochemical cell?

Heating a solution to speed up a reaction

What is the main function of the glass membrane in a pH electrode?

Responds selectively to hydrogen ion (H+) concentration

Which reagent is used in classical gas analysis to absorb oxygen quantitatively?

Pyrogallic acid (pyrogallol)

In thin-layer chromatography (TLC), the relative adsorption of the components in a mixture is expressed in terms of:

Retardation factor (Rf)

The chromatographic (TLC) plate is typically made of:

Glass

In chromatography, the relative solubility of a solute in both the stationary and mobile phases determines the:

Rate of movement of the solute

The elution power (strength) of a solvent in chromatography is primarily determined by its:

Overall polarity

In column chromatography (normal phase, polar stationary phase), the components of a sample are typically eluted in the order of:

Increasing polarity and increasing distribution ratio

Which of the following cannot be used as an adsorbent in column chromatography?

Potassium permanganate

Benzene will be eluted first

An environmental chemist is analyzing air samples to detect low concentrations of pollutant gases. Which of the following techniques would be most appropriate for this type of analysis?

Gas-Solid Chromatography

Ion exchange chromatography is used for all of the following applications, except:

Separation of sugars

Which of the following is not a typical application of a colorimeter?

Identifying chemical composition

A hollow cathode tube lamp is necessary in Atomic Absorption Spectroscopy (AAS) because:

Atom's absorption band is narrow.

Which of the following is an application of molecular spectroscopy?

All of the given answers

Which of the following statements about molecular spectra is correct?

All of the given choices

What is the typical wavelength range of UV radiation in the electromagnetic spectrum?

100 nm to 400 nm

Which of the following is NOT a characteristic of chromophores?

They absorb strongly at 800 nm.

Which compound is most likely to exhibit a strong IR absorption near 1700 cm⁻¹ due to a C=O stretch?

Acetone

Which technique will be most effective at distinguishing between pure samples of isotopic variants?

Mass spectrometry