Question 1

On March 20, 1995, terrorists released an organophosphate nerve gas known as "Sarin" at several points in the Tokyo subway system, killing 11 and injuring more than 5,500 people. Sarin was concealed in lunch boxes and soft-drink containers and placed on subway train floors. It was released as terrorists punctured the containers with umbrellas before leaving the trains. Elemental analysis of Sarin gives the following result: 34.29% C, 7.19% H, 22.84% O, 13.56% F, 22.11% P. How many carbon atoms does the empirical formula of this compound contain?

Accepted Answer

To find the empirical formula, we convert the percentages to moles by dividing by the atomic masses of each element: C (12.01 g/mol), H (1.008 g/mol), O (16.00 g/mol), F (19.00 g/mol), P (30.97 g/mol). This gives us:- C: $34.29 \, \text{g} \div 12.01 \, \text{g/mol} = 2.85 \, \text{mol}$- H: $7.19 \, \text{g} \div 1.008 \, \text{g/mol} = 7.13 \, \text{mol}$- O: $22.84 \, \text{g} \div 16.00 \, \text{g/mol} = 1.43 \, \text{mol}$- F: $13.56 \, \text{g} \div 19.00 \, \text{g/mol} = 0.71 \, \text{mol}$- P: $22.11 \, \text{g} \div 30.97 \, \text{g/mol} = 0.71 \, \text{mol}$To find the empirical formula, we divide each mole value by the smallest mole value found, which is 0.71 in this case. This gives us:- C: $2.85 \div 0.71 = 4$- H: $7.13 \div 0.71 = 10$- O: $1.43 \div 0.71 = 2$- F: $0.71 \div 0.71 = 1$- P: $0.71 \div 0.71 = 1$Thus, the empirical formula contains 4 carbon atoms, placing it in the range of 3 to 6 atoms.

Question 2

A sample of copper(II) sulfate, CuSO₄, that weighs 2.47 grams picks up Water from the atmosphere to form a hydrate with the formula CuSO₄ • x H₂O. If the sample weighs 3.86 grams after it picks up water, what is the value of x?

Accepted Answer

The mass of water added to the copper(II) sulfate is the difference between the final and initial masses, which is 3.86 grams - 2.47 grams = 1.39 grams. The molar mass of copper(II) sulfate (CuSO4) is approximately 159.61 g/mol, and the molar mass of water (H2O) is approximately 18.015 g/mol. The moles of CuSO4 in the initial sample is 2.47 grams / 159.61 g/mol ≈ 0.0155 mol. The moles of water added is 1.39 grams / 18.015 g/mol ≈ 0.0772 mol. The ratio of moles of water to moles of CuSO4 is 0.0772 mol / 0.0155 mol ≈ 5, indicating that the value of x, the number of water molecules per formula unit of CuSO4, is 5.

Question 3

The thermal decomposition of carbonates leads to the loss of CO₂. The decomposition of an unknown carbonate leads to a 35.1% weight loss. The unknown was which of the following compounds.

Accepted Answer

The answer of The thermal decomposition of carbonates leads to...

Question 4

In March of 2007 a number of pets were sickened or killed by pet food contaminated with the chemical melamine which is used in the manufacture of certain plastics. It is thought that the melamine was added to make a pet food additive appear to have more protein than it really did. Melamine is 28.57% C, 4.80% H, and 66.63% N by mass. What is melamine's empirical formula?

Accepted Answer

The empirical formula is determined by converting the percentage composition to moles and finding the simplest whole number ratio. For melamine, the ratio is approximately 1:2:2 for C:H:N, leading to the empirical formula CH₂N₂.

Question 5

In March of 2007 a number of pets were sickened or killed by pet food contaminated with the chemical melamine which is used in the manufacture of certain plastics. It is thought that the melamine was added to make a pet food additive appear to have more protein than it really did. Melamine has the empirical formula CH₂N₂. If the molecular weight of melamine is 126.15 g/mol, what is its molecular formula?

Accepted Answer

The empirical formula mass of CH₂N₂ is 42.04 g/mol. Dividing the molecular weight (126.15 g/mol) by the empirical formula mass gives approximately 3, indicating the molecular formula is C₃H₆N₆.

Question 6

If 0.50 moles of PbS are combined with 0.50 moles of O₂, how many moles of PbO can be produced by the following reaction? 2 PbS(s) + 3 O₂(g) $\rightarrow$ 2 PbO(s) + 2 SO₂(g)

Accepted Answer

The reaction requires 3 moles of O2 for every 2 moles of PbS. With 0.50 moles of each reactant, O2 is the limiting reactant, allowing for only 0.33 moles of PbO to be produced.

Question 7

What would happen to the potential yield of sulfur dioxide in the previous question if the amount of oxygen was doubled?

Accepted Answer

The answer of What would happen to the potential yield...

Question 8

Acetylene gas, C₂H₂, burns in the presence of oxygen by the following reaction: 2 C₂H₂(g) + 5 O₂(g) $\rightarrow$ 2 H₂O(l) + 4 CO₂(g) If 4.5 moles of acetylene gas are to be burned, how many moles of oxygen will be required for the complete reaction of the acetylene?

Accepted Answer

The answer of Acetylene gas, C₂H₂, burns in the presence...

Question 9

For the reaction: 4 NH₃(g) + 5 O₂(g) $\rightarrow$ 4 NO(g) + 6 H₂O(l), how many moles of ammonia, NH₃, are required to react completely with 0.250 moles of oxygen?

Accepted Answer

The answer of For the reaction: 4 NH₃(g) + 5...

Question 10

The molecular formula of isooctane is C₈H₁₈. It burns in the presence of oxygen to form a mixture of CO₂ and H₂O. What is the ratio of moles of water to moles of carbon dioxide produced in this reaction?

Accepted Answer

The answer of The molecular formula of isooctane is C₈H₁₈....

Question 11

A laboratory method for preparing oxygen (O₂) involves the decomposition of KClO₃. KClO₃(s) $\rightarrow$ 2 KCI(s) + 3 O₂(g) How many moles of oxygen are produced when 0.135 moles of KCl are produced by this reaction?

Accepted Answer

The answer of A laboratory method for preparing oxygen (O₂)...

Question 12

What mass of O₂, in grams, is produced in the decomposition of 100 g of KClO₃ by the following reaction? 2 KClO₃(s) $\rightarrow$ 2 KCl(s) + 3 O₂(g)

Accepted Answer

The balanced chemical equation shows that 2 moles of KClO3 produce 3 moles of O2. The molar mass of KClO3 is 122.55 g/mol, and the molar mass of O2 is 32.00 g/mol. Therefore, 100 g of KClO3 will produce (100 g / 122.55 g/mol) * (3 mol O2 / 2 mol KClO3) * (32.00 g/mol O2) = 39.2 g of O2.

Question 13

Iron ore is impure Fe₂O₃. When Fe₂O₃ is heated with an excess of carbon (coke), iron metal is produced. How many moles of Fe can be produced from 250 g of Fe₂O₃ by the following reaction? Fe₂O₃ (s) + 3 C(s) $\rightarrow$ 2 Fe(l) + 3 CO(g)

Accepted Answer

The molar mass of Fe₂O₃ is approximately 159.7 g/mol. 250 g of Fe₂O₃ is equivalent to 250 / 159.7 = 1.57 moles. According to the balanced equation, 1 mole of Fe₂O₃ produces 2 moles of Fe. Therefore, 1.57 moles of Fe₂O₃ will produce 1.57 x 2 = 3.14 moles of Fe, which is approximately 3.13 moles.

Question 14

Calculate the number of moles of iron, Fe, produced when 0.500 moles of carbon monoxide, CO, react with an excess of iron oxide. Fe₂O₃(s) + 3 CO(g) $\rightarrow$ 2 Fe(s) + 3 CO₂(g)

Accepted Answer

The answer of Calculate the number of moles of iron,...

Question 15

Hydrogen chloride, HCI, can be made by the reaction of phosphorus trichloride, PCl₃, with water and then boiling the HCI gas out of the solution. Calculate the mass of HCI gas that can be prepared from 15.0 g of PCl₃ and an excess of water. PCl₃(g) + 3 H₂O(l) $\rightarrow$ 3 HCI(aq) + H₃PO₃(aq)

Accepted Answer

First, correct the chemical formulas: PCl3 + 3 H2O → 3 HCl + H3PO3. The molar mass of PCl3 is approximately 137.33 g/mol. From the given 15.0 g of PCl3, the number of moles of PCl3 is 15.0 g / 137.33 g/mol ≈ 0.109 mol. The reaction shows that 1 mole of PCl3 produces 3 moles of HCl. Therefore, 0.109 mol of PCl3 will produce 0.109 mol × 3 = 0.327 mol of HCl. The molar mass of HCl is approximately 36.46 g/mol, so the mass of HCl gas produced is 0.327 mol × 36.46 g/mol ≈ 11.9 g.

Question 16

Ethyl alcohol, C₂H₅OH, is also known as drinking alcohol. It can be produced by the fermentation of glucose by the following reaction. C₆H₁₂O₆(aq) $\rightarrow$ 2 C₂H₅OH(aq) + 2 CO₂(g) How many $\textbf{ moles }$ of ethanol can be produced from $\textbf{ 100 g }$ of glucose?

Accepted Answer

The molar mass of glucose (C6H12O6) is 180 g/mol. Therefore, 100 g of glucose is 100/180 = 0.556 moles. According to the reaction, 1 mole of glucose produces 2 moles of ethanol, so 0.556 moles of glucose will produce 0.556 * 2 = 1.11 moles of ethanol.

Question 17

Nitrogen reacts with red-hot magnesium to form magnesium nitride, 3 Mg(s) + N₂(g) $\rightarrow$ Mg₃N₂(s) Which reacts with water to form magnesium hydroxide and ammonia, Mg₃N₂(s) + 6 H₂O(l) $\rightarrow$ 3 Mg(OH)₂(aq) + 2 NH₃(aq) How many grams of magnesium would you have to start with to prepare 15.0 grams of ammonia?

Accepted Answer

First, calculate the molar mass of ammonia (NH3): N (14.01 g/mol) + 3*H (3*1.008 g/mol) = 17.034 g/mol. For 15.0 g of NH3, the moles of NH3 are 15.0 g / 17.034 g/mol = 0.8805 mol. From the balanced chemical equation, 1 mol of Mg3N2 produces 2 mol of NH3, so 0.8805 mol NH3 would come from 0.44025 mol of Mg3N2. The molar mass of Mg3N2 is 3*Mg (3*24.305 g/mol) + 2*N (2*14.01 g/mol) = 100.93 g/mol. The moles of Mg needed are 3 times the moles of Mg3N2 because 3 moles of Mg produce 1 mole of Mg3N2, so 0.44025 mol of Mg3N2 corresponds to 1.32075 mol of Mg. The mass of Mg required is 1.32075 mol * 24.305 g/mol = 32.1 g, which rounds to 32.2 g, matching option D.

Question 18

The chemical formula of ethanol is C₂H₆O. It burns in the presence of excess oxygen to form CO₂ and H₂O. How many grams of H₂O are produced from the combustion of 25.0 g of ethanol?

Accepted Answer

The balanced chemical equation for the combustion of ethanol is C2H6O + 3O2 → 2CO2 + 3H2O. The molar mass of ethanol (C2H6O) is 46.08 g/mol. From 25.0 g of ethanol, moles of ethanol = 25.0 g / 46.08 g/mol = 0.542 mol. According to the equation, 1 mol of ethanol produces 3 mol of H2O. Therefore, 0.542 mol of ethanol produces 0.542 * 3 = 1.626 mol of H2O. The molar mass of H2O is 18.02 g/mol, so the mass of H2O produced is 1.626 mol * 18.02 g/mol = 29.3 g.

Question 19

Sucrose, or "cane sugar," has the formula C₁₂H₂₂O₁₁. What weight of carbon dioxide can be produced from 10.0 grams of sucrose and 10.0 grams of oxygen? C₁₂H₂₂O₁₁(s) + 12 O₂(g) $\rightarrow$ 12 CO₂(g) + 11 H₂O(g)

Accepted Answer

10.0 grams of sucrose is 10.0 g / 342.3 g/mol = 0.0292 mol. According to the balanced equation, 0.0292 mol of sucrose will react with 0.350 mol of oxygen and will produce 0.350 mol of carbon dioxide. 0.350 mol of carbon dioxide is 0.350 mol * 44.01 g/mol = 15.4 g.

Question 20

PF₃ reacts with XeF₄ to give PF₅. In theory, how many moles of PF₅ can be produced from 100.0 g of PF₃ and 50.0 g of XeF₄? 2 PF₃(g) + XeF₄(s) $\rightarrow$ 2 PF₅(g) + Xe(g)

Accepted Answer

The answer of PF₃ reacts with XeF₄ to give PF₅....

Quiz 2: The Mole

A sample of copper(II) sulfate, CuSO₄, that weighs 2.47 grams picks up Water from the atmosphere to form a hydrate with the formula CuSO₄ • x H₂O. If the sample weighs 3.86 grams after it picks up water, what is the value of x?

The thermal decomposition of carbonates leads to the loss of CO₂. The decomposition of an unknown carbonate leads to a 35.1% weight loss. The unknown was which of the following compounds.

If 0.50 moles of PbS are combined with 0.50 moles of O₂, how many moles of PbO can be produced by the following reaction? 2 PbS(s) + 3 O₂(g) $\rightarrow$ 2 PbO(s) + 2 SO₂(g)

What would happen to the potential yield of sulfur dioxide in the previous question if the amount of oxygen was doubled?

Acetylene gas, C₂H₂, burns in the presence of oxygen by the following reaction: 2 C₂H₂(g) + 5 O₂(g) $\rightarrow$ 2 H₂O(l) + 4 CO₂(g) If 4.5 moles of acetylene gas are to be burned, how many moles of oxygen will be required for the complete reaction of the acetylene?

For the reaction: 4 NH₃(g) + 5 O₂(g) $\rightarrow$ 4 NO(g) + 6 H₂O(l) , how many moles of ammonia, NH₃, are required to react completely with 0.250 moles of oxygen?

The molecular formula of isooctane is C₈H₁₈. It burns in the presence of oxygen to form a mixture of CO₂ and H₂O. What is the ratio of moles of water to moles of carbon dioxide produced in this reaction?

A laboratory method for preparing oxygen (O₂) involves the decomposition of KClO₃. KClO₃(s) $\rightarrow$ 2 KCI(s) + 3 O₂(g) How many moles of oxygen are produced when 0.135 moles of KCl are produced by this reaction?

What mass of O₂, in grams, is produced in the decomposition of 100 g of KClO₃ by the following reaction? 2 KClO₃(s) $\rightarrow$ 2 KCl(s) + 3 O₂(g)

Iron ore is impure Fe₂O₃. When Fe₂O₃ is heated with an excess of carbon (coke) , iron metal is produced. How many moles of Fe can be produced from 250 g of Fe₂O₃ by the following reaction? Fe₂O₃ (s) + 3 C(s) $\rightarrow$ 2 Fe(l) + 3 CO(g)

Calculate the number of moles of iron, Fe, produced when 0.500 moles of carbon monoxide, CO, react with an excess of iron oxide. Fe₂O₃(s) + 3 CO(g) $\rightarrow$ 2 Fe(s) + 3 CO₂(g)

Ethyl alcohol, C₂H₅OH, is also known as drinking alcohol. It can be produced by the fermentation of glucose by the following reaction. C₆H₁₂O₆(aq) $\rightarrow$ 2 C₂H₅OH(aq) + 2 CO₂(g) How many $\textbf{ moles }$ of ethanol can be produced from $\textbf{ 100 g }$ of glucose?

The chemical formula of ethanol is C₂H₆O. It burns in the presence of excess oxygen to form CO₂ and H₂O. How many grams of H₂O are produced from the combustion of 25.0 g of ethanol?

Sucrose, or "cane sugar," has the formula C₁₂H₂₂O₁₁. What weight of carbon dioxide can be produced from 10.0 grams of sucrose and 10.0 grams of oxygen? C₁₂H₂₂O₁₁(s) + 12 O₂(g) $\rightarrow$ 12 CO₂(g) + 11 H₂O(g)

PF₃ reacts with XeF₄ to give PF₅. In theory, how many moles of PF₅ can be produced from 100.0 g of PF₃ and 50.0 g of XeF₄? 2 PF₃(g) + XeF₄(s) $\rightarrow$ 2 PF₅(g) + Xe(g)

Quiz 2: The Mole

A sample of copper(II) sulfate, CuSO4, that weighs 2.47 grams picks up Water from the atmosphere to form a hydrate with the formula CuSO4 • x H2O. If the sample weighs 3.86 grams after it picks up water, what is the value of x?

The thermal decomposition of carbonates leads to the loss of CO2. The decomposition of an unknown carbonate leads to a 35.1% weight loss. The unknown was which of the following compounds.

If 0.50 moles of PbS are combined with 0.50 moles of O2, how many moles of PbO can be produced by the following reaction? 2 PbS(s) + 3 O2(g) →\rightarrow→ 2 PbO(s) + 2 SO2(g)

What would happen to the potential yield of sulfur dioxide in the previous question if the amount of oxygen was doubled?

Acetylene gas, C2H2, burns in the presence of oxygen by the following reaction: 2 C2H2(g) + 5 O2(g) →\rightarrow→ 2 H2O(l) + 4 CO2(g) If 4.5 moles of acetylene gas are to be burned, how many moles of oxygen will be required for the complete reaction of the acetylene?

For the reaction: 4 NH3(g) + 5 O2(g) →\rightarrow→ 4 NO(g) + 6 H2O(l) , how many moles of ammonia, NH3, are required to react completely with 0.250 moles of oxygen?

The molecular formula of isooctane is C8H18. It burns in the presence of oxygen to form a mixture of CO2 and H2O. What is the ratio of moles of water to moles of carbon dioxide produced in this reaction?

A laboratory method for preparing oxygen (O2) involves the decomposition of KClO3. KClO3(s) →\rightarrow→ 2 KCI(s) + 3 O2(g) How many moles of oxygen are produced when 0.135 moles of KCl are produced by this reaction?

What mass of O2, in grams, is produced in the decomposition of 100 g of KClO3 by the following reaction? 2 KClO3(s) →\rightarrow→ 2 KCl(s) + 3 O2(g)

Iron ore is impure Fe2O3. When Fe2O3 is heated with an excess of carbon (coke) , iron metal is produced. How many moles of Fe can be produced from 250 g of Fe2O3 by the following reaction? Fe2O3 (s) + 3 C(s) →\rightarrow→ 2 Fe(l) + 3 CO(g)

Calculate the number of moles of iron, Fe, produced when 0.500 moles of carbon monoxide, CO, react with an excess of iron oxide. Fe2O3(s) + 3 CO(g) →\rightarrow→ 2 Fe(s) + 3 CO2(g)

Hydrogen chloride, HCI, can be made by the reaction of phosphorus trichloride, PCl3, with water and then boiling the HCI gas out of the solution. Calculate the mass of HCI gas that can be prepared from 15.0 g of PCl3 and an excess of water. PCl3(g) + 3 H2O(l) →\rightarrow→ 3 HCI(aq) + H3PO3(aq)

Ethyl alcohol, C2H5OH, is also known as drinking alcohol. It can be produced by the fermentation of glucose by the following reaction. C6H12O6(aq) →\rightarrow→ 2 C2H5OH(aq) + 2 CO2(g) How many moles \textbf{ moles } moles of ethanol can be produced from 100 g \textbf{ 100 g } 100 g of glucose?

The chemical formula of ethanol is C2H6O. It burns in the presence of excess oxygen to form CO2 and H2O. How many grams of H2O are produced from the combustion of 25.0 g of ethanol?

Sucrose, or "cane sugar," has the formula C12H22O11. What weight of carbon dioxide can be produced from 10.0 grams of sucrose and 10.0 grams of oxygen? C12H22O11(s) + 12 O2(g) →\rightarrow→ 12 CO2(g) + 11 H2O(g)

PF3 reacts with XeF4 to give PF5. In theory, how many moles of PF5 can be produced from 100.0 g of PF3 and 50.0 g of XeF4? 2 PF3(g) + XeF4(s) →\rightarrow→ 2 PF5(g) + Xe(g)

A sample of copper(II) sulfate, CuSO₄, that weighs 2.47 grams picks up Water from the atmosphere to form a hydrate with the formula CuSO₄ • x H₂O. If the sample weighs 3.86 grams after it picks up water, what is the value of x?

The thermal decomposition of carbonates leads to the loss of CO₂. The decomposition of an unknown carbonate leads to a 35.1% weight loss. The unknown was which of the following compounds.

If 0.50 moles of PbS are combined with 0.50 moles of O₂, how many moles of PbO can be produced by the following reaction? 2 PbS(s) + 3 O₂(g) $\rightarrow$ 2 PbO(s) + 2 SO₂(g)

Acetylene gas, C₂H₂, burns in the presence of oxygen by the following reaction: 2 C₂H₂(g) + 5 O₂(g) $\rightarrow$ 2 H₂O(l) + 4 CO₂(g) If 4.5 moles of acetylene gas are to be burned, how many moles of oxygen will be required for the complete reaction of the acetylene?

For the reaction: 4 NH₃(g) + 5 O₂(g) $\rightarrow$ 4 NO(g) + 6 H₂O(l) , how many moles of ammonia, NH₃, are required to react completely with 0.250 moles of oxygen?

The molecular formula of isooctane is C₈H₁₈. It burns in the presence of oxygen to form a mixture of CO₂ and H₂O. What is the ratio of moles of water to moles of carbon dioxide produced in this reaction?

A laboratory method for preparing oxygen (O₂) involves the decomposition of KClO₃. KClO₃(s) $\rightarrow$ 2 KCI(s) + 3 O₂(g) How many moles of oxygen are produced when 0.135 moles of KCl are produced by this reaction?

What mass of O₂, in grams, is produced in the decomposition of 100 g of KClO₃ by the following reaction? 2 KClO₃(s) $\rightarrow$ 2 KCl(s) + 3 O₂(g)

Iron ore is impure Fe₂O₃. When Fe₂O₃ is heated with an excess of carbon (coke) , iron metal is produced. How many moles of Fe can be produced from 250 g of Fe₂O₃ by the following reaction? Fe₂O₃ (s) + 3 C(s) $\rightarrow$ 2 Fe(l) + 3 CO(g)

Calculate the number of moles of iron, Fe, produced when 0.500 moles of carbon monoxide, CO, react with an excess of iron oxide. Fe₂O₃(s) + 3 CO(g) $\rightarrow$ 2 Fe(s) + 3 CO₂(g)

Ethyl alcohol, C₂H₅OH, is also known as drinking alcohol. It can be produced by the fermentation of glucose by the following reaction. C₆H₁₂O₆(aq) $\rightarrow$ 2 C₂H₅OH(aq) + 2 CO₂(g) How many $\textbf{ moles }$ of ethanol can be produced from $\textbf{ 100 g }$ of glucose?

The chemical formula of ethanol is C₂H₆O. It burns in the presence of excess oxygen to form CO₂ and H₂O. How many grams of H₂O are produced from the combustion of 25.0 g of ethanol?

Sucrose, or "cane sugar," has the formula C₁₂H₂₂O₁₁. What weight of carbon dioxide can be produced from 10.0 grams of sucrose and 10.0 grams of oxygen? C₁₂H₂₂O₁₁(s) + 12 O₂(g) $\rightarrow$ 12 CO₂(g) + 11 H₂O(g)

PF₃ reacts with XeF₄ to give PF₅. In theory, how many moles of PF₅ can be produced from 100.0 g of PF₃ and 50.0 g of XeF₄? 2 PF₃(g) + XeF₄(s) $\rightarrow$ 2 PF₅(g) + Xe(g)