Midterm Review S2

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

Tags

NGSS.HS-PS1-7

A student is supplied with the following data and asked to determine the composition of three unknown compounds containing iron and sulfur (Fe_xS_y). 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 FeS_1.5. 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 Fe_0.67S. 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 Fe_0.67S. 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 FeS_1.5. 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%

Tags

NGSS.HS-PS1-7

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

Tags

NGSS.HS-PS1-7

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%

Tags

NGSS.HS-PS1-7

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.

Tags

NGSS.HS-PS1-7

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.

Tags

NGSS.HS-PS1-7