A scientist decided to use high-tech equipment to measure the electronegativity, an atom's attraction to electrons, of the second period on the periodic table. The results of her measurements are in the chart below. Z is equal to the atomic number of the specified atom and the number of protons in that atom.

According to the experimenter's measurements, what is the apparent relationship between number of protons and the electronegativity of an atom?

A scientist decided to use high-tech equipment to measure the electronegativity, an atom's attraction to electrons, of the second period on the periodic table. The results of her measurements are in the chart below. Z is equal to the atomic number of the specified atom and the number of protons in that atom.

What is the apparent relationship between an atom's atomic number Z and its likelihood to attract electrons from a source of electrons?

Solutions are made by dissolving a solute into a solvent. Different types of solvents have varying levels of solubility, or ability to dissolve certain substances. 

A student decided to conduct an experiment to compare the solubilities of different solvents at different temperatures using table salt (sodium chloride) as a solute. The student would keep an amount of solvent at the specified temperature and add solute until no more solute would dissolve. This is amount or solute is called the point of saturation. The amount added to each solvent at saturation was recorded. The results of the experiment are shown in the tables: 

Table 1:

Table 2:

Based on the data, which solvent involved in the experiment has the greatest solubility?

A free energy reaction diagram shows the energy of a chemical reaction as it progresses from start to finish. In Example 1 below, the reactants (at point A) start with a certain energy. Energy is then applied to initiate the reaction (this is called activation energy) and the reaction progresses to point B. Lastly, energy is released in the reaction leading to point C. If the net change in free energy of a reaction is positive, the reaction is called a nonspontaneous reaction, meaning that it takes more energy to initiate it than the energy released. If the net change in free energy of a reaction is negative, it is called spontaneous, meaning that the energy released is more than the energy needed to initiate the reaction. 

Example 1:

What can we conclude about Example 1 above given the information in the passage?

Solutions are made by dissolving a solute into a solvent. Different types of solvents have varying levels of solubility, or ability to dissolve certain substances. 

A student decided to conduct an experiment to compare the solubilities of different solvents at different temperatures using table salt (sodium chloride) as a solute. The student would keep an amount of solvent at the specified temperature and add solute until no more solute would dissolve. This is amount or solute is called the point of saturation. The amount added to each solvent at saturation was recorded. The results of the experiment are shown in the tables: 

Table 1:

Table 2:

What is the apparent relationship between temperature and solubility?

A chemist has mixed up the labels on some of his chemical compounds. To try to determine the compounds, the chemist dissolves the compounds in pure water. He notes the pH, corrosiveness and the color of each solution. 

Assume that all of the substances can clean surfaces. Which of the substances will clean most surfaces without wrecking the surface? 

If a drug is taken orally, then the concentration of that drug in the blood will rise to a peak concentration. Immediately afterwards, the elimination phase begins and the concentration of the drug in the body will fall exponentially. Each drug has a half-life (i.e. the time required for the drug's concentration in the blood to fall to half of its original value). Once the elimination phase has initiated, it typically takes four half-lives until the drug has been entirely eliminated from the body.

If an individual is given multiple doses of a drug over time, then the blood concentration of the drug will rise and fall periodically. This creates a graph of drug’s concentration versus time that will resemble a wave. The rising peaks of the graph occur immediately after administration of a dose, whereas the falling valleys occur as the drug is being eliminated. The inter-dose interval, represented by the letter , is defined as the time (in hours) between doses of the drug.

Experiment 1

A 125-milligram oral dose of a drug known as Cyclosporin A (CsA) was administered to an individual. The CsA blood concentration for this individual was then measured at various times over the next 24 hours. A graph of CsA concentration versus time was obtained.

Experiment 2

An individual was given multiple doses of CsA over a 60-hour period. The CsA blood concentration was monitored continuously. A graph of CsA concentration versus time was obtained.

Based on the results of Experiment 2 and information in the passage, what was the inter-dose interval of CsA?

If a drug is taken orally, then the concentration of that drug in the blood will rise to a peak concentration. Immediately afterwards, the elimination phase begins and the concentration of the drug in the body will fall exponentially. Each drug has a half-life (i.e. the time required for the drug's concentration in the blood to fall to half of its original value). Once the elimination phase has initiated, it typically takes four half-lives until the drug has been entirely eliminated from the body.

If an individual is given multiple doses of a drug over time, then the blood concentration of the drug will rise and fall periodically. This creates a graph of drug’s concentration versus time that will resemble a wave. The rising peaks of the graph occur immediately after administration of a dose, whereas the falling valleys occur as the drug is being eliminated. The inter-dose interval, represented by the letter , is defined as the time (in hours) between doses of the drug.

Experiment 1

A 125-milligram oral dose of a drug known as Cyclosporin A (CsA) was administered to an individual. The CsA blood concentration for this individual was then measured at various times over the next 24 hours. A graph of CsA concentration versus time was obtained.

Experiment 2

An individual was given multiple doses of CsA over a 60-hour period. The CsA blood concentration was monitored continuously. A graph of CsA concentration versus time was obtained.

Based on the results of Experiment 1 and the information in the passage, at which point does the elimination phase of CsA begin (assume the first data point is at zero hours)?

If a drug is taken orally, then the concentration of that drug in the blood will rise to a peak concentration. Immediately afterwards, the elimination phase begins and the concentration of the drug in the body will fall exponentially. Each drug has a half-life (i.e. the time required for the drug's concentration in the blood to fall to half of its original value). Once the elimination phase has initiated, it typically takes four half-lives until the drug has been entirely eliminated from the body.

If an individual is given multiple doses of a drug over time, then the blood concentration of the drug will rise and fall periodically. This creates a graph of drug’s concentration versus time that will resemble a wave. The rising peaks of the graph occur immediately after administration of a dose, whereas the falling valleys occur as the drug is being eliminated. The inter-dose interval, represented by the letter , is defined as the time (in hours) between doses of the drug.

Experiment 1

A 125-milligram oral dose of a drug known as Cyclosporin A (CsA) was administered to an individual. The CsA blood concentration for this individual was then measured at various times over the next 24 hours. A graph of CsA concentration versus time was obtained.

Experiment 2

An individual was given multiple doses of CsA over a 60-hour period. The CsA blood concentration was monitored continuously. A graph of CsA concentration versus time was obtained.

Suppose drug administration had continued past 60 hours during Experiment 2. Based on the results of Experiment 2, what would be the most likely concentration of CsA at 66 hours (assume the drug continued to be administered in the same exact way)? 

A chemist has found five substances in his lab without specific labels, named only A, B, C, D, and E. He hopes to find clues about the identity of each substance by dissolving each in hexane, a nonpolar solvent. He adds each substance to a different  sample of hexane until no more can be dissolved. This is dubbed the point of saturation.

Which substance has the highest solubility in hexane?