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Example Questions
Example Question #71 : Chemistry
Two scientists wanted to test the solubility of different substances. Solubility is a measure of how many moles of a given substance (known as the solute) can dissolve in a given volume of another substance (known as the solvent). The solvent can also be thought of as the substance present in greater amount, while the solute can be seen as the substance present in lesser amount. The scientists performed the following experiments to investigate this property.
Experiment 1
The scientists tested the number of moles of several substances that could be completely dissolved in 
Table 1
Experiment 2
In this experiment, the scientists wanted to test the solubility of 
Table 2
How did the procedures of the two experiments differ?
In Experiment 1, several solutes were tested, while Experiment 2 tested several solvents.
In Experiment 1, temperature was held constant, while in Experiment 2, temperature was varied.
There was no difference between experimental procedures for Experiments 1 and 2.
In Experiment 1, several solvents were tested, while Experiment 2 tested several solutes.
In Experiment 1, temperature was varied, while in Experiment 2, it was held constant.
In Experiment 1, several solutes were tested, while Experiment 2 tested several solvents.
This question requires a careful reading of the text, or a good understanding of the definition of solutes and solvents. We can eliminate the choices dealing with temperature, because a cursory glance at Table 1 and Table 2 reveals that temperature was varied in both experiments.
A solvent is the substance present in greater amount. In this passage, all our solvents are liquids.
A solute is the substance present in smaller amount. In this case, our solutes are solids.
In Experiment 1, several solids were tested, while in Experiment 2, only one solid was tested: 
Example Question #72 : Chemistry
Two scientists wanted to test the solubility of different substances. Solubility is a measure of how many moles of a given substance (known as the solute) can dissolve in a given volume of another substance (known as the solvent). The solvent can also be thought of as the substance present in greater amount, while the solute can be seen as the substance present in lesser amount. The scientists performed the following experiments to investigate this property.
Experiment 1
The scientists tested the number of moles of several substances that could be completely dissolved in 
Table 1
Experiment 2
In this experiment, the scientists wanted to test the solubility of 
Table 2
Why did the scientists weigh the beakers before adding any solutes to them?
By weighing the beakers first, the scientists could find the added mass by subtracting the initial mass.
By weighing the beakers first, the scientists could make sure their balance was working properly.
The scientists weighed the beakers beforehand in order to know how much of each solute to add.
The scientists weighed the beakers beforehand in order to make sure their beakers weren't damaged.
By weighing the beakers first, the scientists could find the added mass by subtracting the initial mass.
When weighing out anything in chemistry, it is important to be very precise. Reading through the description of Experiment 1, we find the following: "The beakers were weighed before and after the additions and the difference in mass was calculated to be the added mass of the substance." This suggests that finding the mass of the beakers before adding any solute was done in order to find the mass that was added. By taking the difference between the original mass (without any solute) and the final mass, the scientists could find the added amount of solute, and from that, the number of moles of solute added. This means the correct answer choice is, "By weighing the beakers first, the scientists could find the added mass by subtracting the initial mass."
Example Question #73 : Chemistry
Two scientists wanted to test the solubility of different substances. Solubility is a measure of how many moles of a given substance (known as the solute) can dissolve in a given volume of another substance (known as the solvent). The solvent can also be thought of as the substance present in greater amount, while the solute can be seen as the substance present in lesser amount. The scientists performed the following experiments to investigate this property.
Experiment 1
The scientists tested the number of moles of several substances that could be completely dissolved in
Table 1
Experiment 2
In this experiment, the scientists wanted to test the solubility of
Table 2
Suppose the scientists conducted a third experiment in which they dissolved 
This question requires some careful reading and extrapolation. We want to find the number of grams dissolved in
In experiment two, we need two details to guide us.
1) 
2) The highest temperature tested for methanol was 
So, the scientists had 
So, we can eliminate any answers lower than or equal to 
Example Question #12 : How To Find Experimental Design In Chemistry
The rate of a reaction is defined as the rate at which the products of a reaction are produced. A researcher wants to investigate the rate of reaction of the combustion of theoretical compound 
The results of the experiment are shown in the table below. The brackets ([]) indicate concentration measured in mol/L.
Which of the following is the best explanation for the repetition of trial 1 during the experiment?
Repeating trial 1 revealed that the results of trials 2 and 3 were due to chance.
Repeating trial 1 did not serve any purpose.
Repeating trial 1 ensured the original results of trial 1 were due to chance.
Repeating trial 1 caused the reactions measured in trials 2 and 3.
Repeating trial 1 acted as a control.
Repeating trial 1 acted as a control.
This question is a bit tricky because it can be easy to get distracted with the other answers. If you go back into the passage, you see that the researcher expressed concern that the lab's conditions could change and therefore could affect measurements. Therefore, repeating trial 1 during the experiment was simply a control to account for possible changes in the lab that could affect the results. As it states in the passage, the researcher's concerns were unfounded, and repeating trial 1 was indeed unnecessary. However, that does not mean that it did not serve the purpose of proving to the researcher that the conditions of the lab stayed steady throughout the experiment—which is well worth the additional effort.
Example Question #762 : Act Science
The above chemical equation describes the dissociation of carbonic acid 
When carbon dioxide 
To study this effect, the student obtains a mixture of carbonic acid, bicarbonate, and hydrogen ion. Next, the student conducts trials in which she adds a certain amount of one of the chemicals one at a time and then measures how the concentrations of each chemical change after each addition.
What can we infer would happen if the student were to add hydrochloric acid (a source of hydrogen ions) into a flask of a predetermined amount of carbonic acid, bicarbonate, and hydrogen ion?
The concentrations would not change.
Both the concentration of bicarbonate and carbonic acid would decrease.
The concentration of bicarbonate would decrease and the concentration of carbonic acid would increase.
The concentration of bicarbonate would increase, and the concentration of carbonic acid would decrease.
Both the concentration of bicarbonate and carbonic acid would increase.
The concentration of bicarbonate would decrease and the concentration of carbonic acid would increase.
For this question, we must have a firm understanding of the passage's description of equilibrium. In summary, the passage states that adding more of a chemical on one half of the chemical equation will shift equilibrium to the other direction. Therefore, if we add more hydrogen ion with hydrochloric acid, we know that equilibrium will shift left. This would mean that more carbonic acid would form, so it would increase while decreasing the amount of bicarbonate ion.
Example Question #763 : Act Science
Kevin wants to know if a particular kind of chemical fertilizer will help or hinder the growth of his tomato plants. He decides to conduct an experiment in which he grows three plants, one left untreated, one treated with the chemical fertilizer RapidGro and one treated with an organic compost. He records his findings in the charts below, measuring plant height and number of tomatoes over a period of time.
Height of plant (inches):
|
Day |
No Fertilizer |
RapidGro |
Compost |
|
1 |
3 |
3 |
3 |
|
2 |
5 |
6 |
4 |
|
3 |
7 |
9 |
6 |
|
4 |
9 |
12 |
8 |
|
7 |
15 |
21 |
14 |
|
10 |
16 |
21 |
19 |
|
14 |
18 |
18 |
21 |
Number of tomatoes:
|
Day |
No fertilizer |
RapidGro |
Compost |
|
1 |
0 |
0 |
0 |
|
2 |
1 |
2 |
1 |
|
3 |
1 |
3 |
2 |
|
4 |
2 |
4 |
3 |
|
7 |
4 |
7 |
5 |
|
10 |
6 |
7 |
6 |
|
14 |
6 |
4 |
7 |
On the fourteenth day Kevin picks the biggest tomato from each plant and record its dimensions, as well as other information, which is found below.
Tomato 1 (no fertilizer): 
Tomato 2 (RapidGro): 
Tomato 3 (compost): 
Which plant is the control?
The plant with compost
The plant with chemical fertilizer
There is no control
The plant without fertilizer or compost
The plant without fertilizer or compost
In an experiment, the control is what does not change or remains untreated by the variables being tested, in this case the fertilizer or compost.
Example Question #761 : Act Science
The Environmental Protection Agency compiled the following information about heavy metals in drinking water. Heavy metals are toxic, and thus must be monitored very closely. All amounts are given in parts per billion (ppb), a common measurement of concentration for trace contaminants. Figure 1 shows total heavy metal contamination in each city as a makeup of various percentages of specific contaminants. Figure 2 shows specific amounts of contaminants (with the same color coding) in ppb as well as total contamination level in ppb.
Figure 1
Figure 2
Which city has the most total cadmium in parts per billion?
Fargo
Boston
Chicago
Miami
Boston
Figure 2, which shows total amount of contamination by contaminant, indicates cadmium contamination in yellow. Note that the yellow bar for Boston is clearly the largest, indicating 2.5ppb of cadmium.
Example Question #81 : Chemistry
The Environmental Protection Agency compiled the following information about heavy metals in drinking water. Heavy metals are toxic, and thus must be monitored very closely. All amounts are given in parts per billion (ppb), a common measurement of concentration for trace contaminants. Figure 1 shows total heavy metal contamination in each city as a makeup of various percentages of specific contaminants. Figure 2 shows specific amounts of contaminants (with the same color coding) in ppb as well as total contamination level in ppb.
Figure 1
Figure 2
Which contaminant is most abundant in Fargo?
Beryllium
Lead
Mercury
Cadmium
Mercury
Either chart (the pie chart labeled Fargo, or the bar for Fargo on the bar graph) shows that the green contaminant, mercury, is the most abundant. Antimony, shown in red, may be a close second, however, this answer choice is not available.
Example Question #766 : Act Science
The Environmental Protection Agency compiled the following information about heavy metals in drinking water. Heavy metals are toxic, and thus must be monitored very closely. All amounts are given in parts per billion (ppb), a common measurement of concentration for trace contaminants. Figure 1 shows total heavy metal contamination in each city as a makeup of various percentages of specific contaminants. Figure 2 shows specific amounts of contaminants (with the same color coding) in ppb as well as total contamination level in ppb.
Figure 1
Figure 2
A scientist wants to publish a paper about water treatment standards in the United States. Which figure is a better figure to include in her report?
Figure 2, because it shows both relative amounts of each contaminant in various cities, and also because it shows numerical amounts of each contaminant in ppb.
Figure 2, because it shows which cities have the most total contamination.
Figure 1, because it shows the numerical amounts of each contaminant in ppb, a useful metric.
Figure 1, because it shows percent contamination most clearly, and this is the most important piece of data for contamination studies.
Figure 2, because it shows both relative amounts of each contaminant in various cities, and also because it shows numerical amounts of each contaminant in ppb.
Figure 2 shows the relative amounts of each contaminant. For example, you can see that Fargo clearly has more mercury contamination, shown in green, than Boston, by comparing the relative heights of the green part of the two bars. The figure also shows numerical amounts of contaminant in ppb on the y-axis. We can see the amount of each contaminant in each city in ppb or the total amount of contamination in ppb.
Figure 1 shows relative contaminant amounts as a percentage of the total of each city's total contamination. It gives no data whatsoever about numerical parts per billion contaminant concentrations. This second type of information is probably more important for scientists to truly understand the degree of contamination in each of these cities.
While Figure 2 does show which cities have the most total contamination, it is not the sole reason that Figure 2 is the more useful figure. The other statement about Figure 2 is a more complete answer.
It is true that Figure 1 shows percent contamination more clearly than Figure 2. However, as Figure 2 imparts more information in total, including percentage information, it is more useful. Additionally, percent contamination of a total wherein the totals for each city differ does not give a lot of information that can be compared city to city.
Example Question #763 : Act Science
Naturally occurring water in lakes and reservoirs used as sources for drinking water feature a variety of dissolved minerals such as magnesium, sodium, and calcium. Water treatment plants must closely monitor the levels of these minerals to ensure they do not exceed unsafe levels. An experiment carried out by a scientist at a water treatment plant are described below.
Experiment 1:
A common way to determine the concentration of a particular chemical is by titration. In this titration, 10mL of the treated water sample was placed in a flask as shown below in Figure 1. A buret, (a special funnel with volume markings on the side and a knob on the bottom to control how much of the substance in the buret is dispensed) was placed above the flask as shown in Figure 1. It was filled with 50mL of a 20ppm (parts per million) solution of EDTA, a chemical that can react with magnesium to chemically remove it from the water. An indicator (a substance that changes color to indicate a chemical change) was also placed into the flask; this indicator appears purple in water solutions containing magnesium, and blue in water solutions without magnesium. The buret was used to dispense EDTA solution until enough EDTA had been added to the purple magnesium-containing water solutions to remove all the magnesium and turn the solution blue. The volume, in milliliters, of EDTA solution added to each of five water samples is recorded in Table 1.
Figure 1
The formula for parts per million (ppm) of magnesium 
We see from Table 1 that the average volume of EDTA solution added is approximately 30mL. Use this value and the given equation to solve for the parts per million of magnesium.
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