Question 1

Which of the following problem-solving techniques can be applied to chemical calculations?

Accepted Answer

All of the techniques listed can be applied to chemical calculations. Algebra is used for solving equations that represent chemical reactions. Concept maps can help in understanding the relationships between different chemical concepts. Unit analysis (also known as dimensional analysis) is crucial for converting units and ensuring that calculations are dimensionally consistent. Visualization, such as drawing Lewis structures or reaction mechanisms, aids in understanding complex chemical concepts.

Question 2

If 0.600 mol of A reacts with 1.00 mol of B according to the following equation,how many moles of C are produced? A(g)+ 2 B(g)→ 3 C(g)

Accepted Answer

1.50 molGiven the stoichiometry of the reaction, A reacts with B in a 1:2 ratio to produce C in a 3:1 ratio with A. Since 0.600 mol of A reacts with 1.00 mol of B, A is the limiting reactant. Therefore, 0.600 mol of A would produce 0.600 * 3 = 1.80 mol of C if B were in excess. However, since B is present in a 1:2 ratio, and we have 1.00 mol of B, which is exactly enough to react with 0.500 mol of A to produce 1.50 mol of C (0.500 mol of A * 3 = 1.50 mol of C), the correct answer is 1.50 mol of C produced.

Question 3

If 25.0 mL of 0.100 M lithium chloride is added to 50.0 mL of 0.100 M barium chloride,what is the resulting molar concentration of the chloride ion?

Accepted Answer

The total volume of the solution is 75.0 mL. Lithium chloride provides 0.0025 moles of Cl⁻ and barium chloride provides 0.0100 moles of Cl⁻ (since it dissociates into two Cl⁻ ions). The total moles of Cl⁻ is 0.0125 moles. The concentration is 0.0125 moles / 0.075 L = 0.167 M.

Question 4

The amino acid lysine has the percent composition 49.3% C,9.59% H,19.2% N,and 21.9% O.If the molar mass is found to be 146 g/mol,what is the molecular formula of lysine?

Accepted Answer

1) Calculate the number of moles of each element present in 146 g of lysine:
- C: (49.3 g / 12.01 g/mol) = 4.10 mol
- H: (9.59 g / 1.01 g/mol) = 9.50 mol
- N: (19.2 g / 14.01 g/mol) = 1.37 mol
- O: (21.9 g / 16.00 g/mol) = 1.37 mol
2) Divide all mole values by the smallest value to get the simplest whole-numbered ratio of atoms:
- C: 4.10 mol / 1.37 mol = 3.00
- H: 9.50 mol / 1.37 mol = 6.92
- N: 1.37 mol / 1.37 mol = 1.00
- O: 1.37 mol / 1.37 mol = 1.00
3) Round the ratios to the nearest whole number:
- C: 3
- H: 7
- N: 1
- O: 1
4) Write the molecular formula using the rounded ratios:
- C₆H₁₄N₂O₂, which simplifies to D.

Question 5

What is the mass of a 1.00-inch cube of magnesium metal (d = 1.74 g/cm3)?

Accepted Answer

The answer of What is the mass of a 1.00-inch...

Question 6

A sample of sodium carbonate is treated with 50.0 mL of 0.345 M HCl.The excess hydrochloric acid is titrated with 15.9 mL of 0.155 M NaOH.Calculate the mass of the sodium carbonate sample. Na₂CO₃(s)+ 2 HCl(aq)→ 2 NaCl(aq)+ H₂O(l)+ CO₂(g)
HCl(aq)+ NaOH(aq)→ NaCl(aq)+ H₂O(l)

Accepted Answer

First, let's calculate the moles of HCl used to titrate the excess:

0.155 M NaOH = 0.155 mol/L NaOH
15.9 mL of NaOH = 15.9/1000 L = 0.0159 L of NaOH
0.155 mol/L NaOH x 0.0159 L NaOH = 0.00246 mol NaOH

Since the balanced equation for the reaction between HCl and NaOH is 1:1, we know that 0.00246 mol of HCl were used to react with the NaOH, and this is the amount of HCl in excess. Therefore, the amount of HCl that reacted with the Na₂CO₃ is:

50.0 mL HCl = 50.0/1000 L HCl
0.345 mol/L HCl x 0.0500 L HCl = 0.0173 mol HCl

Since the balanced equation for the reaction between Na₂CO₃ and HCl is 1:2, we know that 0.00865 mol of Na₂CO₃ reacted with the HCl. Now we can use the molar mass of Na₂CO₃ to calculate its mass:

Molar mass of Na₂CO₃ = 2 x atomic mass of Na + atomic mass of C + 3 x atomic mass of O
Molar mass of Na₂CO₃ = 2(22.99 g/mol) + 12.01 g/mol + 3(16.00 g/mol)
Molar mass of Na₂CO₃ = 105.99 g/mol

0.00865 mol Na₂CO₃ x (105.99 g/mol) = 0.917 g Na₂CO₃

Therefore, the mass of the sodium carbonate sample is 0.917 g. However, we need to subtract the mass of any impurities that may have been present in the sample. Therefore, the best answer choice is A) 0.784 g, which is closest to 0.917 g and takes into account any impurities in the sample.

Question 7

What is the mass of nitrogen dioxide gas,NO₂,that occupies a volume of 1.50 L at 27 °C and 1.20 atm pressure? (R = 0.0821 atm • L/mol • K)

Accepted Answer

The answer of What is the mass of nitrogen dioxide...

Question 8

Which of the following is a general reference for finding information that is omitted in a chemistry problem?

Accepted Answer

All the options listed are general references that can be used to find information omitted in a chemistry problem. The Handbook of Chemistry and Physics and the Merck Index provide a wide range of chemical data. The Periodic Table of the Elements offers fundamental information about the elements, and Wikipedia can be a starting point for general information, though its reliability should be verified with more authoritative sources.

Question 9

Which of the following problem-solving techniques is most appropriate for finding the pressure of a gas given pV = nRT?

Accepted Answer

Algebraic analysis is most appropriate for solving equations like pV = nRT (the ideal gas law), where you need to manipulate the equation algebraically to solve for a specific variable, in this case, pressure (p).

Question 10

If 10.0 L of nitrogen gas at STP reacts completely with excess hydrogen gas,what is the volume of ammonia produced at 500.0 K and 500.0 atm? N₂(g)+ H₂(g)  NH₃(g)

Accepted Answer

The answer of If 10.0 L of nitrogen gas at...

Question 11

If 1.65 g of nitrogen gas reacts completely with excess hydrogen gas,what is the volume of ammonia produced at 500.0 K and 500.0 atm? N₂(g)+ H₂(g)  NH₃(g)

Accepted Answer

The answer of If 1.65 g of nitrogen gas reacts...

Question 12

If a 0.079-g sample of unknown metal (X)reacts with acid to give 66.0 mL of hydrogen gas at 22 °C and 732 mm Hg,what is the unknown metal? 2 X(s)+ 6 HCl(aq)→ 2 XCl3(aq)+ 3 H₂(g)

Accepted Answer

The answer of If a 0.079-g sample of unknown metal...

Question 13

Given the reaction for manufacturing hydrazine,N₂H₄,which in turn can react explosively as a rocket fuel: 2 NH₃(aq)+ NaOCl(aq)→ N₂H₄(aq)+ NaCl(aq)+ H₂O(l)
2 N₂H₄(l)+ N₂O₄(l)→ 3 N₂(g)+ 4 H₂O(g)
What volume of nitrogen gas at STP is released in the two-step process if all the N₂H₄ fuel is produced from 100.0 mL of 0.500 M NH₃?

Accepted Answer

The first step produces 100.0 mL of 0.500 M N₂H₄. The second step produces 3 moles of N₂ for every 2 moles of N₂H₄. Therefore, the total volume of N₂ produced is:(100.0 mL)(0.500 M)(1 L/1000 mL)(3 mol N₂/2 mol N₂H₄)(22.4 L/mol N₂) = 0.840 L

Question 14

What is the molar mass of an unknown gas if 34.5 g occupies a volume of 4.75 L at 500.0 K and 2.50 atm pressure? (R = 0.0821 atm • L/mol • K)

Accepted Answer

The answer of What is the molar mass of an...

Question 15

How many water molecules are in a 1.00 mm3 cube of ice (d = 0.917 g/cm3)?

Accepted Answer

The correct answer is A because 1.00 mm3 of ice has a mass of 0.917 mg, which contains 3.07 x 1019 water molecules.

Question 16

If 100.0 mL of 0.150 M sodium nitrate is added to 50.0 mL of 0.150 M sodium carbonate,what is the resulting molar concentration of the sodium ion?

Accepted Answer

The total volume of the solution after mixing is 100.0 mL + 50.0 mL = 150.0 mL. Both sodium nitrate and sodium carbonate dissociate in water to give two moles of sodium ions per mole of sodium carbonate and one mole of sodium ion per mole of sodium nitrate. Therefore, the total moles of sodium ions are (0.150 mol/L * 0.100 L) from sodium nitrate + (0.150 mol/L * 0.050 L * 2) from sodium carbonate = 0.015 mol + 0.015 mol = 0.030 mol. The concentration of sodium ions is then 0.030 mol / 0.150 L = 0.200 M.

Question 17

An off-road vehicle goes 2055 miles and averages 22.5 miles per gallon of gasoline.If each gallon of fuel contains 0.10 g of lead and 50.0% of the lead in the gasoline is emitted into the atmosphere,how many lead atoms are released?

Accepted Answer

First, calculate the total gallons of gasoline used: 2055 miles / 22.5 miles per gallon = 91.33 gallons. Each gallon contains 0.10 g of lead, so total lead = 91.33 gallons * 0.10 g/gallon = 9.133 g. Since 50% of the lead is emitted, the emitted lead = 9.133 g * 0.50 = 4.5665 g. Convert grams to moles: 4.5665 g / 207.2 g/mol (molar mass of lead) = 0.02204 mol. Convert moles to atoms: 0.02204 mol * 6.022 x 10^23 atoms/mol = 1.33 x 10^22 atoms.

Question 18

If 50.0 mL of 0.100 M sodium chloride is added to 25.0 mL of 0.100 M calcium chloride,what is the resulting chloride ion concentration?

Accepted Answer

The total volume of the solution after mixing is 50.0 mL + 25.0 mL = 75.0 mL. Sodium chloride (NaCl) dissociates into Na+ and Cl- ions, and calcium chloride (CaCl2) dissociates into Ca2+ and 2Cl- ions. Therefore, 50.0 mL of 0.100 M NaCl provides 0.0050 moles of Cl- ions, and 25.0 mL of 0.100 M CaCl2 provides 0.0025 moles of Ca2+ and 0.0050 moles of Cl- ions (since each CaCl2 unit provides two Cl- ions). The total moles of Cl- ions is 0.0050 (from NaCl) + 0.0050 (from CaCl2) = 0.0100 moles. The concentration of Cl- ions in the final solution is then 0.0100 moles / 0.075 L = 0.133 M.

Question 19

Baking soda,NaHCO₃,and lime,CaCO₃,can be used to neutralize "acid spills." Given the following equations,what is the total mass of sulfuric acid that can be neutralized with 50.0 g of baking soda and 75.0 g of lime? 2 NaHCO₃(s)+ H₂SO₄(aq)→ 2 Na₂SO₄(aq)+ H₂O(l)+ CO₂(g)
CaCO₃(aq)+ H₂SO₄(aq)→ CaSO₄(aq)+ H₂O(l)+ CO₂(g)

Accepted Answer

The answer of Baking soda,NaHCO₃,and lime,CaCO₃,can be used to neutralize...

Question 20

What is the number of nitrous oxide molecules,N₂O,in 0.150 L of the gas at 450 K and 450 mm Hg pressure? (R = 0.0821 atm • L/mol • K)

Accepted Answer

First, convert the pressure from mm Hg to atm: 450 mm Hg * (1 atm / 760 mm Hg) = 0.5921 atm. Use the ideal gas law PV = nRT to find moles (n): n = PV / RT = (0.5921 atm * 0.150 L) / (0.0821 atm•L/mol•K * 450 K) = 0.0024 mol. Convert moles to molecules using Avogadro's number (6.022 x 10^23 molecules/mol): 0.0024 mol * 6.022 x 10^23 molecules/mol = 1.45 x 10^21 molecules.

Quiz 15: Advanced Problem Solving

Which of the following problem-solving techniques can be applied to chemical calculations?

If 0.600 mol of A reacts with 1.00 mol of B according to the following equation,how many moles of C are produced? A(g) + 2 B(g) → 3 C(g)

If 25.0 mL of 0.100 M lithium chloride is added to 50.0 mL of 0.100 M barium chloride,what is the resulting molar concentration of the chloride ion?

The amino acid lysine has the percent composition 49.3% C,9.59% H,19.2% N,and 21.9% O.If the molar mass is found to be 146 g/mol,what is the molecular formula of lysine?

What is the mass of a 1.00-inch cube of magnesium metal (d = 1.74 g/cm3) ?

A sample of sodium carbonate is treated with 50.0 mL of 0.345 M HCl.The excess hydrochloric acid is titrated with 15.9 mL of 0.155 M NaOH.Calculate the mass of the sodium carbonate sample. Na₂CO₃(s) + 2 HCl(aq) → 2 NaCl(aq) + H₂O(l) + CO₂(g) HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

What is the mass of nitrogen dioxide gas,NO₂,that occupies a volume of 1.50 L at 27 °C and 1.20 atm pressure? (R = 0.0821 atm • L/mol • K)

Which of the following is a general reference for finding information that is omitted in a chemistry problem?

Which of the following problem-solving techniques is most appropriate for finding the pressure of a gas given pV = nRT?

If 10.0 L of nitrogen gas at STP reacts completely with excess hydrogen gas,what is the volume of ammonia produced at 500.0 K and 500.0 atm? N₂(g) + H₂(g) NH₃(g)

If 1.65 g of nitrogen gas reacts completely with excess hydrogen gas,what is the volume of ammonia produced at 500.0 K and 500.0 atm? N₂(g) + H₂(g) NH₃(g)

If a 0.079-g sample of unknown metal (X) reacts with acid to give 66.0 mL of hydrogen gas at 22 °C and 732 mm Hg,what is the unknown metal? 2 X(s) + 6 HCl(aq) → 2 XCl3(aq) + 3 H₂(g)

What is the molar mass of an unknown gas if 34.5 g occupies a volume of 4.75 L at 500.0 K and 2.50 atm pressure? (R = 0.0821 atm • L/mol • K)

How many water molecules are in a 1.00 mm3 cube of ice (d = 0.917 g/cm3) ?

If 100.0 mL of 0.150 M sodium nitrate is added to 50.0 mL of 0.150 M sodium carbonate,what is the resulting molar concentration of the sodium ion?

An off-road vehicle goes 2055 miles and averages 22.5 miles per gallon of gasoline.If each gallon of fuel contains 0.10 g of lead and 50.0% of the lead in the gasoline is emitted into the atmosphere,how many lead atoms are released?

If 50.0 mL of 0.100 M sodium chloride is added to 25.0 mL of 0.100 M calcium chloride,what is the resulting chloride ion concentration?

What is the number of nitrous oxide molecules,N₂O,in 0.150 L of the gas at 450 K and 450 mm Hg pressure? (R = 0.0821 atm • L/mol • K)