ACT Science : How to find data representation in chemistry

Study concepts, example questions & explanations for ACT Science

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Example Questions

Example Question #51 : How To Find Data Representation In Chemistry

Solubility and temp

According to the graph at what temperature, in degrees celsius, are the solubilities for  and  the same?

Possible Answers:

Between 30 and 40

Between 10 and 20

Between 40 and 50

Between 70 and 80

Between 60 and 70

Correct answer:

Between 40 and 50

Explanation:

On the graph  and  intersect between 40 and 50 degrees celsius.

Example Question #52 : How To Find Data Representation In Chemistry

Solubility and temp

Based on the data in the graph, at   the solubility of  would most likely be which of these?

Possible Answers:

Between  and 

Between  and 

Greater than 

Greater than 

Less than 

Correct answer:

Greater than 

Explanation:

Assuming that the continuous positive slope of  solubility persists, the solubility of  will be over greater than .

Example Question #52 : How To Find Data Representation In Chemistry

The table lists some of the properties of row 2 elements in the periodic table.

Atomic radius table

What conclusion can be drawn from the data in regards to atomic radius in row 2 elements on the periodic table?

Possible Answers:

An element with a low atomic radius will have low electonegativity

An element with a low atomic radius will have a low atomic number

An element with a high atomic radius will have high electronegativity

An element with a low atomic radius will be a metal

An element with a high atomic radius will be a metal

Correct answer:

An element with a high atomic radius will be a metal

Explanation:

From studying the table it can be seen that the elements with the top two highest atomic radii are metals. As the atomic radius decreases elements are non-metals.

Example Question #51 : Chemistry

The table lists some of the properties of row 2 elements in the periodic table.

Atomic radius table

Which of the following graphs best represents the relationship between atomic radius and electronegativity for row 2 elements?

Possible Answers:

Atomic radius table ans3

Atomic radius table ans2

Atomic radius table ans4

Atomic radius table ans1

Atomic radius table ans5

Correct answer:

Atomic radius table ans2

Explanation:

The table shows that as the atomic radius increases the electronegativity decreases. However, the atomic radius does not increase in continuous increments but in fact increases in larger subsequent increments as electronegativity decreases. Therefore, the graph will contain a curved line with a negative slope instead of a straight line.

Example Question #733 : Act Science

Assuming that all of the weight lost or gained were solely from fat, determine the calories lost for the group subjected to only Inhibitor II. The energy density of fat is 9 calories per gram.

Possible Answers:

37,000 calories

22,000 calories

14,000 calories

31,000 calories

27,000 calories

Correct answer:

27,000 calories

Explanation:

The approximate weight loss is about 3 kg for the Inhibitor II group. Therefore

Example Question #53 : How To Find Data Representation In Chemistry

Compute the mass of the fatty acid produced if inhibitor II were present in a sample of FAS and the experiment were to run for 20 seconds. Assume the fatty acid being produced is oleic acid, with a molecular weight of 282 grams.

Possible Answers:

.0021 grams

.0056 grams

.0087 grams

.0093 grams

.0014 grams

Correct answer:

.0056 grams

Explanation:

Given that the rate of FAS with Inhibitor II present is  (Table 1), we can estimate this number to about . Knowing that the experiment runs for 20 seconds, and that a micro is a , we know that:

Moles produced = 

We can then compute the molecular weight by simply multiplying the number of moles by the molecular weight (282 grams), yielding 0.0056 grams.

Example Question #731 : Act Science

A student performed the following procedures to study various photosynthetic pigments (light-absorbing chemicals) in tree leaves and the wavelengths of light they absorb.

Experiment 1:

The student obtained samples of leaves from oaks, maples, ashes, sycamores, and poplars. Each leaf sample was ground separately with a mortar and pestle to release the pigments, and then each sample was suspended in water to make a colored solution of the pigment. The student then measured the absorption spectrum (a graph of how much light is absorbed by a pigment at varying wavelengths of light) of each solution in a device called a spectrophotometer. The setup of a spectrophotometer is shown below in Diagram 1.

 

 Spectrophotometer

 

The light source emits white light, which is split into its various wavelengths by the prism. Next, a slit, which can be moved up or down to select a particular wavelength, is used to transmit just a single wavelength to the sample. The sample absorbs a fraction of this light that is characteristic to the pigment in the sample, and the rest is transmitted to the detector for a readout. Using the spectrophotometer, the student found the λmax (the wavelength of light in nanometers (nm) that the pigment absorbs most intensely, for each sample) and recorded the results in Table 1. Table 1 also shows the transmittance and absorbance values at λmax. Transmittance, T, is defined as the fraction of light, expressed as a decimal, which passes through the sample. Absorbance, A, is given by:

                                    A = –log(T)   or  10–A = T

 

 Spectrophotometer_table_1

 

Experiment 2:

A student is given a leaf from an unknown source. She crushes and extracts the pigment according to the procedure in Experiment 1. Measuring the absorbance spectrum in the spectrophotometer produces the following readout, shown in Diagram 2.

 Leaf_absorbance

                                                Diagram 2

Which of the following leaves most likely have the same pigment in high quantities?

Possible Answers:

Maple and Sycamore

Oak and Ash

Oak and Sycamore

Maple and Ash

Correct answer:

Oak and Ash

Explanation:

The description of Experiment 1 states that λmax is a value characteristic of a particular pigment. Because λmax = 436nm for both Oak and Ash leaves, it can be assumed that this is because both leaves contain large amounts of the same pigment.

Example Question #51 : Chemistry

A student performed the following procedures to study various photosynthetic pigments (light-absorbing chemicals) in tree leaves and the wavelengths of light they absorb.

Experiment 1:

The student obtained samples of leaves from oaks, maples, ashes, sycamores, and poplars. Each leaf sample was ground separately with a mortar and pestle to release the pigments, and then each sample was suspended in water to make a colored solution of the pigment. The student then measured the absorption spectrum (a graph of how much light is absorbed by a pigment at varying wavelengths of light) of each solution in a device called a spectrophotometer. The setup of a spectrophotometer is shown below in Diagram 1.

 

 Spectrophotometer

 

The light source emits white light, which is split into its various wavelengths by the prism. Next, a slit, which can be moved up or down to select a particular wavelength, is used to transmit just a single wavelength to the sample. The sample absorbs a fraction of this light that is characteristic to the pigment in the sample, and the rest is transmitted to the detector for a readout. Using the spectrophotometer, the student found the λmax (the wavelength of light in nanometers (nm) that the pigment absorbs most intensely, for each sample) and recorded the results in Table 1. Table 1 also shows the transmittance and absorbance values at λmax. Transmittance, T, is defined as the fraction of light, expressed as a decimal, which passes through the sample. Absorbance, A, is given by:

                                    A = –log(T)   or  10–A = T

 

 Spectrophotometer_table_1

 

Experiment 2:

A student is given a leaf from an unknown source. She crushes and extracts the pigment according to the procedure in Experiment 1. Measuring the absorbance spectrum in the spectrophotometer produces the following readout, shown in Diagram 2.

 Leaf_absorbance

                                                Diagram 2

What is λmax, in nanometers, for the leaf in Experiment 2?

Possible Answers:

630

440

0.9

0.6

Correct answer:

440

Explanation:

Experiment 1 states that λmax is the wavelength at which light is absorbed most intensely. Thus, we can look for the wavelength, found on the x-axis of Diagram 2, that produces the highest absorbance, found on the y-axis. This value is 440 nm, which produces an absorbance of 0.9. 

Example Question #742 : Act Science

A student wanted to study the kinetics, or rates of a chemical reaction based on the concentrations of its reactants and products, of the reaction shown below.

 

This reaction is easy to monitor using a spectrophotometer, which measures how much light of a particular wavelength is absorbed by a solution. The deep purple potassium permanganate, or , absorbs light of a 550 nm wavelength in proportion to its concentration in the reaction solution. Manganese sulfate, or , is pale pink and absorbs light of a 500 nm wavelength in proportion to its concentration in the reaction solution. All other reactants and products are colorless and do not absorb visible light and thus cannot be monitored using the spectrophotometer.

 

Experiment 1:

The student constructed a standard curve, or a graph of the absorbance of solutions of varying concentrations of potassium permanganate, to quantify the relationship between concentration and absorbance. To prepare five sample of increasing concentration, he labeled five test tubes A, B, C, D, and E, weighed out 0.1, 0.2, 0.3, 0.4, and 0.5 grams of potassium permanganate into each, respectively, and added 1 milliliter (mL) of water to each test tube to dissolve. Then, he used the spectrophotometer to determine the absorbance at 550 nm of each sample. The data is graphed in Figure 1 below.

Kinetics_figure_1 

                                                        Figure 1

  

Experiment 2: 

The student then studied potassium permanganate in the presence of oxalic acid, , to observe the reaction. Monitoring both the absorbances of potassium permanganate and manganese sulfate, he was able to determine the reaction rate using a special setting on the spectrophotometer. The reaction rate at various concentrations of reactants is shown below in Table 1.

Kinetics_table_2

A sample solution of potassium permanganate in 1 milliliter of water was placed in a spectrophotometer and evaluated for its absorbance at 550 nm. It gave an absorbance of 0.3. How many grams of potassium permanganate were dissolved in the sample?

Possible Answers:


Correct answer:


Explanation:

Figure 1 shows the relationship between absorbance and concentration of potassium permanganate. Look for the absorbance value of 0.3 on the vertical axis and see what concentration value on the horizontal axis would produce such an absorbance. The answer is 1.5 grams/mL. As the sample in this problem was dissolved in the same amount of water as in Experiment 1, we can assume that 0.15 grams were dissolved in this sample.

Example Question #54 : Chemistry

A student wanted to study the kinetics, or rates of a chemical reaction based on the concentrations of its reactants and products, of the reaction shown below.

 

This reaction is easy to monitor using a spectrophotometer, which measures how much light of a particular wavelength is absorbed by a solution. The deep purple potassium permanganate, or , absorbs light of a 550 nm wavelength in proportion to its concentration in the reaction solution. Manganese sulfate, or , is pale pink and absorbs light of a 500 nm wavelength in proportion to its concentration in the reaction solution. All other reactants and products are colorless and do not absorb visible light and thus cannot be monitored using the spectrophotometer.

 

Experiment 1:

The student constructed a standard curve, or a graph of the absorbance of solutions of varying concentrations of potassium permanganate, to quantify the relationship between concentration and absorbance. To prepare five sample of increasing concentration, he labeled five test tubes A, B, C, D, and E, weighed out 0.1, 0.2, 0.3, 0.4, and 0.5 grams of potassium permanganate into each, respectively, and added 1 milliliter (mL) of water to each test tube to dissolve. Then, he used the spectrophotometer to determine the absorbance at 550 nm of each sample. The data is graphed in Figure 1 below.

Kinetics_figure_1 

                                                        Figure 1

  

Experiment 2: 

The student then studied potassium permanganate in the presence of oxalic acid, , to observe the reaction. Monitoring both the absorbances of potassium permanganate and manganese sulfate, he was able to determine the reaction rate using a special setting on the spectrophotometer. The reaction rate at various concentrations of reactants is shown below in Table 1.

Kinetics_table_2

Which of the following graphs could potentially generated if absorbance at 550 nm was graphed over time for a mixture of potassium permanganate and oxalic acid?

Kinetics_q6

Possible Answers:

Green graph

Purple graph

Red graph

Blue graph

Correct answer:

Red graph

Explanation:

As the absorbance is monitored at 550 nm, which will observe the behavior of potassium permanganate, a reactant, we know the absorbance should decrease as time goes on. The concentration of a reactant will decrease as it is used up by the reaction. Thus, the answer must be the red graph, as it is the only graph that shows consistently decreasing absorbance.

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