WorksheetsMidterm Review S2
Total questions: 20
Worksheet time: 15mins
Which substances have the same empirical formula and why?
Samples 1 and 4 because the ratio of C:H:O in these compounds is 1:4:1 representing the simplest ratio of these elements in one molecule of the compound
Samples 2 and 4 because the formulas contain carbon, hydrogen, and oxygen in the simplest ratio possible
Samples 1 and 4 because the ratio of C:H:O in these compounds is 1:4:1, meaning that the number of carbon atoms added to the number of oxygen atoms in the molecule equals the number of hydrogen atoms
Samples 2 and 4 because the ratio of C:H:O in these compounds is 1:2:1 representing the simplest ratio of these elements in one molecule of the compound
A student calculated the number of moles of carbon dioxide present in a 100.0 gram sample of a gaseous mixture. If the student determined that there's 0.30 moles of carbon dioxide present in the sample, what is the percent composition of carbon dioxide in the sample?
13%
0.30%
0.13%
30%
Two samples were massed and the data is listed below. A student also carried out calculations to find the number of atoms and moles in the sample.
Sample 1: 11 g Na; 6.02 x 1023 atoms; 1 mole
Sample 2: 2.0 g of He; 3.01 x 1023 atoms; 0.5 moles
Using the data above, which sample data correctly identifies how mass, mole, and grams are related.
Sample 1 data is correct because 11 protons have the mass of 11 grams which equals 1 mole which is 6.02 x 1023 atoms
Sample 2 data is correct because half of the atomic mass would = half of 6.02 x 1023 atoms and half of a mole
Sample 1 data is correct because the atomic mass equals 1 mole which is 6.02 x 1023 atoms
Sample 2 data is correct because 2 protons equals 6.02 x 1023 atoms which is 1 mole
A student is supplied with the following data and asked to determine the composition of three unknown compounds containing iron and sulfur (FexSy). The student interprets the data table below and concludes that:
Sample 1 is FeS; Sample 2 is FeS2; Sample 3 has a composition that is not a whole number and therefore must have arisen from some error.
The student’s professor tells the student that the interpretation of Sample 3’s data is incorrect. Which statement best describes the student’s error with the correct reasoning?
The student believed Sample 3 to have a composition of FeS1.5. The correct empirical formula is Fe2S3. The student did not multiply the determined chemical formula to yield whole numbers.
The student believed Sample 3 to have a composition of Fe0.67S. The correct empirical formula is FeS. The student did not round his digits to the nearest whole number.
The student believed Sample 3 to have a composition of Fe0.67S. The correct empirical formula is Fe4S6. The student did not multiply the determined chemical formula to yield whole numbers.
The student believed sample 3 to have a composition of FeS1.5. The correct empirical formula is FeS2. The student did not round his digits to the nearest whole number.
P4 + 6Cl2 → 4PCl3
The reaction of 75 g P4 with 40 g chlorine gas produces 110 g PCl3 in lab. Calculate percent yield for the reaction.
68.2%
1.045%
104.5%
95.6%
Based on the mole ratios in the table provided, which is the correct reaction for the chemical equation?
3A + 4B --> 2C
4A + 2B --> C
3A + 4B --> 4C
2A + 4B --> 4C
A student is conducting a laboratory experiment with sulfur hexafluoride. However, the student did not complete the required pre-laboratory notes.
Compound: SF6
Mass: 235.7 g
Which selection would help the student complete the requisite notes?
1.6 moles, 9.72 x1023 particles
0.62 moles, 9.72 x1023 particles
1.6 moles, 2.65 x1022 particles
0.62 moles, 2.65 x1022 particles
Copper metal and silver nitrate complete a single replacement reaction according to the balanced equation below:
Cu + 2AgNO3 → Cu(NO3)2 + 2Ag
In a particular reaction between copper metal and silver nitrate, 12.7 g Cu produced 38.1 g Ag. What is the percent yield of silver in this reaction?
56.7%
77.3%
88.2%
176%
A student carries out the following reaction:
2 Fe (s) + 3 S (g) → Fe2S3 (s)
The student determines that 0.32 moles of Iron (III) sulfide were produced, resulting in a 76% yield. How could the student determine the initial amount of sulfur used?
Determine the moles of iron (III) sulfide if 100 percent were reacted by placing 24% equal to 0.32 moles/x and then convert moles of iron (III) sulfide to moles of sulfur using the mole ratio of 3:1.
Determine the moles of iron (III) sulfide if 100 percent were reacted by placing 76% equal to 0.32 moles/x and then converting moles iron (III) sulfide to moles of sulfur using the mole ratio of 3:1.
Convert moles of Iron (III) sulfide to moles of Sulfur using the mole ratio of 3:1.
Convert moles of Iron (III) sulfide to moles of Sulfur using the mole ratio of 1:3.
A combustion reaction is given below:
C5H12(l) + 8O2(g) → 5CO2(g) + 6H2O(g)
Which of the following is true about the total number of reactants and the total number of products in the reaction shown below?
9 moles of reactants chemically change into 11 moles of product.
9 grams of reactants chemically change into 11 grams of product.
9 kilograms of reactants chemically change into 11 grams of product.
9 atoms of reactants chemically change into 11 atoms of product.
A classic chemistry class demonstration is the burning of magnesium ribbon with a Bunsen burner. In this demonstration, two chemical reactions are occurring: the burning of methane gas and the reaction between oxygen and magnesium. Of the two reactions, what is the only limiting reactant?
Methane gas from the gas supply
Oxygen consumed by combustion in the Bunsen burner
Oxygen that combines with the burning magnesium
Magnesium ribbon that is burned
Fe + Cl2 → FeCl2
A student wants to demonstrate the concept of limiting reactants to his labmates during class. If the student adds 56 g of Fe to 71 g of Cl2, what will the likely result of the reaction be in regards to limiting/excess reactants?
Although there is more Cl2, it takes two takes chlorine atoms to react with every one iron atom, so iron will be the excess reagent and chlorine will be the limiting reagent
There is an equal amount of iron and chloride, so the reactants will be fully consumed with neither limiting nor in excess
There is an equal amount of iron and chloride; however, because of the 1:2 Fe:Cl nature of the reaction, iron will be in excess and chlorine will be the limiting reagent
Since the molar mass of each respective compound is approximately the mass used for the experiment, both will be fully consumed with neither limiting nor in excess.
Four students are developing a model to illustrate covalent and ionic substances dissolving in water. They each write down what they think is the most important difference between covalent and ionic compounds dissolving in water. Which student has the best understanding of what the model needs to illustrate?
Student A: Water is a polar molecule and has a partially positive end and a partially negative end. This will be important to show when ionic compounds dissolve but not covalent.
Student B: Ionic compounds dissociate into ions and so it will be important to show the ions floating around in the water.
Student C: Covalent molecules stay together as a unit so it will be important to show the polar water attracting to different areas of the covalent molecule.
Student D: Polar water molecules will surround a covalent molecule and separate it from other covalent molecules. The polar water will separate the positive and negative ions from each other in an ionic compound.
Which statement best describes what happens during dissociation process?
KCl is surrounded by the polar H2O to form an electrolyte solution which can conduct electricity.
KCl is surrounded by the nonpolar H2O to form an electrolyte solution which can conduct electricity.
Positive and negative ions attract in the presence of water to allow the potassium cation to be pulled away from the chloride anion and go into solution.
Since,”like dissolves like” the anion of KCl will be attracted to the anion of water and allow the KCl to dissolve and go into solution.
In class students were given the pictures below and asked to pick a solution that would conduct electricity and to justify their choice.
Based on the model, Which student’s argument is correct?
Student A claims that left beaker contains an ionic compound because the solute breaks apart into charged particles.
Student B claims that the left beaker contains a covalent compound because the solute breaks apart into charged particles.
Student C claims that the right beaker contains an ionic compound because the solute stays together when dissolved.
Student D claims to identify the solute as either ionic or covalent more information is needed than what is provided in the model.
Which of these would NOT increase the rate of dissolving?
shaking/stirring the mixture causing an increase in rate of dissolution
grinding the solute to increase the surface area
decreasing the pressure so that a gas dissolves in the solution
increasing the temperature in order to increase molecule collisions
Saline (salt) solution is 0.9% by mass which is similar to tears, blood, and other body fluids. Which of the following might be the recipe used in commercial saline solutions?
0.9 g of salt and 91 g water
0.9 g of salt and 99.1 g water
0.9 g of salt and 100 g water
0.9 g of salt and 100.9 g water
How would you prepare a 1 L solution of 3 M MgO?
Dissolve 3 moles of MgO in 1 L of water.
Place 120 g of MgO in a 1000 mL volumetric flask and add enough water to reach the 1 L mark.
Place 120 g of MgO in a 1000mL volumetric flask and add 1 L of water to the beaker
Dissolve 3 grams of MgO in 1 L of water.
If more powdered Kool Aid is added to the same amount of water, what happens to the solution?
The molarity of the solution decreases because there are more particles in the solution.
The molarity of the solution increases because there are more particles in the solution.
The solution becomes more dilute there is less water in the solution.
The solution becomes unsaturated because there is more water than Kool Aid in the solution.
Vinegars can be 5-20% acetic acid solutions and has been used for medicinal purposes for thousands of years. If a person takes 2 Tablespoons of vinegar a day and the molarity of the vinegar is 0.84 M, then how many grams of acetic acid (HC2H3O2) will be consumed? 1 Tablespoon is 15 mL.
0.013 g
0.026 g
0.76 g
1.51 g
