Question 1

What is the oxidation number of the sulfur atom in K₂SO₄?

Accepted Answer

The answer of What is the oxidation number of the...

Question 2

Balance the chemical equation given below, and determine the number of moles of iodine that reacts with 30.0 g of aluminum. ________ Al(s)+ ________ I₂(s)→ ________ Al₂I₆(s)

Accepted Answer

The balanced chemical equation is:

2 Al(s) + 3 I2(s) → 2 AlI3(s)

From the equation, we can see that 3 moles of I2 react with 2 moles of Al. Therefore, we can use a mole ratio to determine the number of moles of I2 required to react with 30.0 g of Al:

30.0 g Al x (1 mol Al/26.98 g) x (3 mol I2/2 mol Al) x (253.8 g I2/1 mol I2) = 1.67 mol I2

Therefore, the correct choice is B.

Question 3

Lithium and nitrogen react to produce lithium nitride: 6Li(s)+ N₂(g)→ 2Li₃N(s) How many moles of lithium nitride are produced when 0.450 mol of lithium react in this fashion?

Accepted Answer

The balanced equation shows that 6 moles of lithium produce 2 moles of lithium nitride. Therefore, 0.450 moles of lithium will produce (0.450 mol Li) * (2 mol Li3N / 6 mol Li) = 0.150 mol of lithium nitride.

Question 4

Lithium and nitrogen react to produce lithium nitride: 6Li(s)+ N₂(g)→ 2Li₃N(s) How many moles of N₂ are needed to react with 0.500 mol of lithium?

Accepted Answer

The answer of Lithium and nitrogen react to produce lithium...

Question 5

What is the oxidation number of the chromium atom in K₂CrO₄?

Accepted Answer

The first step is to identify the oxidation numbers of the other elements in the compound:

- K has an oxidation state of +1 
- O has an oxidation state of -2 
- S has an oxidation state of -2

Let x be the oxidation state of Cr, then we can set up the equation: 
+1 - 2x - 2 - 2 - 2 - 2 + 2x - 14 - 2 = 0 
Simplifying: 
-18 + 2x = 0 
2x = +18 
x = +9

However, this answer is incorrect as it is highly improbable that chromium would have an oxidation state of +9.

The correct answer can be found by realizing that this is an ionic compound made up of K+ and the polyatomic ion CrO4^2-. 
The overall charge of the compound must be 0, so: 
+1 + x - 8 = 0 
Simplifying: 
x = +7 
Therefore, the oxidation state of the chromium atom in this compound is +6 (Choice C).

Question 6

How many millilitres of 0.132 mol L^-1 HClO₄ solution are needed to neutralize 50.00 mL of 0.0789 mol L^-1 NaOH?

Accepted Answer

To neutralize NaOH with HClO4, use the formula: (C1)(V1) = (C2)(V2). Here, C1 = 0.132 mol/L, C2 = 0.0789 mol/L, and V2 = 50.00 mL. Solving for V1 gives V1 = (0.0789 mol/L * 50.00 mL) / 0.132 mol/L = 29.9 mL.

Question 7

What is the oxidation number change for the bromine atom in the following unbalanced reduction half-reaction: BrO₃^-(aq)+ H⁺(aq)→ Br^-(aq)+ H₂O(l)

Accepted Answer

Before the reaction, the oxidation number of Br is 0. In the product, the oxidation number of Br is -1. Therefore, the oxidation number change for Br is -1.

Question 8

What are the coefficients in front of NO₃^-(aq)and Cu(s)when the following redox equation is balanced in an acidic solution? ___ NO₃^-(aq)+ ___ Cu(s)→ ___ NO(g)+ ___ Cu²⁺(aq)?

Accepted Answer

In order to balance the equation, the number of electrons lost by Cu must equal the number of electrons gained by NO₃^-(aq). This requires the coefficient of Cu to be 3 and the coefficient of NO₃^-(aq) to be 2. Therefore, the coefficients in front of Cu and NO₃^-(aq) are 3 and 2, respectively.

Question 9

What is the oxidation number of the oxygen atom in Na₂O₂?

Accepted Answer

The sulfur atom has an oxidation number of -2 in this compound (based on its usual oxidation state of -2 in sulfides) and there are three sulfur atoms in the compound. Therefore, the total negative charge contributed by the sulfur atoms is -6. Since the compound is neutral, the total positive charge contributed by the other elements must be +6. There is only one oxygen atom in the compound, and it is bonded to sulfur, which has an oxidation number of -2. Therefore, the oxygen atom must have an oxidation number of -1 in order to balance out the charge.

Question 10

How many grams of calcium chloride are needed to produce 1.50 g of potassium chloride? CaCl₂(aq)+ K₂CO₃(aq)→ 2KCl(aq)+ CaCO₃(aq)

Accepted Answer

The balanced chemical equation is CaCl2(aq) + K2CO3(aq) → 2 KCl(aq) + CaCO3(aq). To find the grams of CaCl2 needed to produce 1.50 g of KCl, we use stoichiometry. The molar mass of KCl is approximately 74.55 g/mol, so 1.50 g of KCl is 1.50 g / 74.55 g/mol = 0.0201 mol. Since the reaction produces 2 moles of KCl for every 1 mole of CaCl2, we need 0.0201 mol / 2 = 0.01005 mol of CaCl2. The molar mass of CaCl2 is approximately 110.98 g/mol, so the mass of CaCl2 needed is 0.01005 mol * 110.98 g/mol = 1.12 g.

Question 11

How many moles of BCl₃ are needed to produce 10.0 g of HCl(aq)in the following reaction? BCl₃(g)+ 3H₂O(l)→ 3HCl(aq)+ B(OH)₃(aq)

Accepted Answer

1. Calculate the molar mass of BCl₃: B: 10.81 g/mol Cl: 35.45 g/mol S: 32.06 g/mol BCl₃ = 10.81 g/mol + 35.45 g/mol + 3(32.06 g/mol) + 2(15.99 g/mol) = 208.94 g/mol 2. Calculate the number of moles of HCl using its molar mass: H: 1.01 g/mol Cl: 35.45 g/mol HCl = 1.01 g/mol + 35.45 g/mol = 36.46 g/mol n(HCl) = m(HCl) / MM(HCl) = 10.0 g / 36.46 g/mol = 0.274 mol 3. Use the stoichiometry of the balanced equation to find the number of moles of BCl₃ needed: 3 mol HCl / 1 mol BCl₃ n(BCl₃) = n(HCl) / (3 mol HCl / 1 mol BCl₃) = 0.274 mol / (3 mol / 1) = 0.0914 mol

Question 12

What is the molarity of a NaOH solution if 28.2 mL of a 0.355 mol L^-1 H₂SO₄ solution is required to neutralize a 25.0 mL sample of the NaOH solution?

Accepted Answer

The correct answer is A because the number of moles of H2SO4 used is equal to the number of moles of NaOH present in the 25.0 mL sample. Therefore, the molarity of the NaOH solution can be calculated as follows:Molarity of NaOH = (Molarity of H2SO4 * Volume of H2SO4 used) / Volume of NaOH solutionMolarity of NaOH = (0.355 mol L-1 * 28.2 mL) / 25.0 mLMolarity of NaOH = 0.801 mol L-1

Question 13

Automotive air bags inflate when sodium azide decomposes explosively to its constituent elements: 2NaN₃(s)→ 2Na(s)+ 3N₂(g) How many grams of sodium azide are required to produce 33.0 g of nitrogen?

Accepted Answer

1 mol of nitrogen is produced from 2 moles of NaNO3
33g of nitrogen will be produced from (33/28) * (2/3) *  NaN3
= 51.1 g NaN3 (approx)

Question 14

How many moles of CuO can be produced from 0.900 mol of Cu₂O in the following reaction? 2Cu₂O(s)+ O₂(g)→ 4CuO(s)

Accepted Answer

According to the balanced chemical equation, 2 moles of Cu₂O produces 4 moles of CuO. Therefore, 0.900 mol of Cu₂O will produce (4/2)*0.900 = 1.80 mol of CuO.

Question 15

Lithium and nitrogen react in a combination reaction to produce lithium nitride: 6Li(s)+ N₂(g)→ 2Li₃N(s) How many moles of lithium are needed to produce 0.60 mol of Li₃N when the reaction is carried out in the presence of excess nitrogen?

Accepted Answer

The answer of Lithium and nitrogen react in a combination...

Question 16

Balance the chemical equation given below, and determine the number of grams of MgO needed to produce 10.0 g of Fe₂O₃. ________ MgO(s)+ ________ Fe(s)→ ________ Fe₂O₃(s)+ ________ Mg(s)

Accepted Answer

The answer of Balance the chemical equation given below, and...

Question 17

Automotive air bags inflate when sodium azide decomposes explosively to its constituent elements: 2NaN₃(s)→ 2Na(s)+ 3N₂(g) How many moles of N₂ are produced by the decomposition of 2.88 mol of sodium azide?

Accepted Answer

From the balanced equation, we can see that 2 moles of sodium azide produce 3 moles of N₂. Therefore, 2.88 mol of sodium azide will produce: 3/2 x 2.88 mol = 4.32 mol of N₂ The answer is (C) 4.32.

Question 18

Magnesium burns in air with a dazzling brilliance to produce magnesium oxide: 2Mg(s)+ O₂(g)→ 2MgO(s) When 4.00 g of magnesium burns, what is the theoretical yield of magnesium oxide?

Accepted Answer

To find the theoretical yield, we need to use stoichiometry.

First, we convert the mass of magnesium to moles using its molar mass:
4.00 g Mg * (1 mol Mg/24.31 g Mg) = 0.165 mol Mg

Next, we use the balanced chemical equation to determine the mole ratio between magnesium and magnesium oxide:
2Mg(s) + O2(g) → 2MgO(s)
2 mol Mg : 2 mol MgO

So for every 2 moles of magnesium that reacts, 2 moles of magnesium oxide is produced. Therefore:
0.165 mol Mg * (2 mol MgO/2 mol Mg) = 0.165 mol MgO

Finally, we convert the moles of magnesium oxide to grams using its molar mass:
0.165 mol MgO * (40.31 g MgO/1 mol MgO) = 6.63 g MgO

Therefore, the theoretical yield of magnesium oxide is 6.63 g, which is answer choice B.

Question 19

Dinitrogen monoxide gas decomposes to form nitrogen gas and oxygen gas. How many grams of oxygen are formed when 10.0 g of dinitrogen monoxide decomposes?

Accepted Answer

The balanced chemical equation for the decomposition of dinitrogen monoxide is:

N2O(g) → N2(g) + O2(g)

Using the molar masses of N2O (44 g/mol) and O2 (32 g/mol), we can calculate the number of moles of O2 produced:

10.0 g N2O × (1 mol N2O/44 g N2O) × (1 mol O2/1 mol N2O) × (32 g O2/1 mol O2) = 3.64 g O2

Therefore, 3.64 g of oxygen gas are formed.

Question 20

Magnesium burns in air with a dazzling brilliance to produce magnesium oxide: 2Mg(s)+ O₂(g)→ 2MgO(s) How many moles of O₂ are consumed when 0.770 mol of magnesium burns?

Accepted Answer

From the balanced chemical equation, we see that the mole ratio between magnesium and oxygen gas is 2:1. Therefore, for every 2 moles of magnesium that reacts, 1 mole of oxygen gas is consumed. 
In this problem, we are given 0.770 mol of magnesium, so we need to determine how many moles of oxygen gas are consumed. 
(0.770 mol Mg) x (1 mol O2 / 2 mol Mg) = 0.385 mol O2 
Therefore, the answer is choice E, 0.385.

Quiz 4: Chemical Reactions and Stoichiometry

What is the oxidation number of the sulfur atom in K₂SO₄?

Balance the chemical equation given below, and determine the number of moles of iodine that reacts with 30.0 g of aluminum. Al(s) + I₂(s) → Al₂I₆(s)

Lithium and nitrogen react to produce lithium nitride: 6Li(s) + N₂(g) → 2Li₃N(s) How many moles of lithium nitride are produced when 0.450 mol of lithium react in this fashion?

Lithium and nitrogen react to produce lithium nitride: 6Li(s) + N₂(g) → 2Li₃N(s) How many moles of N₂ are needed to react with 0.500 mol of lithium?

What is the oxidation number of the chromium atom in K₂CrO₄?

How many millilitres of 0.132 mol L^-1 HClO₄ solution are needed to neutralize 50.00 mL of 0.0789 mol L^-1 NaOH?

What is the oxidation number change for the bromine atom in the following unbalanced reduction half-reaction: BrO₃^-(aq) + H⁺(aq) → Br^-(aq) + H₂O(l)

What are the coefficients in front of NO₃^-(aq) and Cu(s) when the following redox equation is balanced in an acidic solution? _ NO₃^-(aq) + _ Cu(s) → _ NO(g) + _ Cu²⁺(aq) ?

What is the oxidation number of the oxygen atom in Na₂O₂?

How many grams of calcium chloride are needed to produce 1.50 g of potassium chloride? CaCl₂(aq) + K₂CO₃(aq) → 2KCl(aq) + CaCO₃(aq)

How many moles of BCl₃ are needed to produce 10.0 g of HCl(aq) in the following reaction? BCl₃(g) + 3H₂O(l) → 3HCl(aq) + B(OH) ₃(aq)

What is the molarity of a NaOH solution if 28.2 mL of a 0.355 mol L^-1 H₂SO₄ solution is required to neutralize a 25.0 mL sample of the NaOH solution?

Automotive air bags inflate when sodium azide decomposes explosively to its constituent elements: 2NaN₃(s) → 2Na(s) + 3N₂(g) How many grams of sodium azide are required to produce 33.0 g of nitrogen?

How many moles of CuO can be produced from 0.900 mol of Cu₂O in the following reaction? 2Cu₂O(s) + O₂(g) → 4CuO(s)

Lithium and nitrogen react in a combination reaction to produce lithium nitride: 6Li(s) + N₂(g) → 2Li₃N(s) How many moles of lithium are needed to produce 0.60 mol of Li₃N when the reaction is carried out in the presence of excess nitrogen?

Balance the chemical equation given below, and determine the number of grams of MgO needed to produce 10.0 g of Fe₂O₃. MgO(s) + Fe(s) → Fe₂O₃(s) + Mg(s)

Automotive air bags inflate when sodium azide decomposes explosively to its constituent elements: 2NaN₃(s) → 2Na(s) + 3N₂(g) How many moles of N₂ are produced by the decomposition of 2.88 mol of sodium azide?

Magnesium burns in air with a dazzling brilliance to produce magnesium oxide: 2Mg(s) + O₂(g) → 2MgO(s) When 4.00 g of magnesium burns, what is the theoretical yield of magnesium oxide?

Dinitrogen monoxide gas decomposes to form nitrogen gas and oxygen gas. How many grams of oxygen are formed when 10.0 g of dinitrogen monoxide decomposes?

Magnesium burns in air with a dazzling brilliance to produce magnesium oxide: 2Mg(s) + O₂(g) → 2MgO(s) How many moles of O₂ are consumed when 0.770 mol of magnesium burns?

Quiz 4: Chemical Reactions and Stoichiometry

What is the oxidation number of the sulfur atom in K2SO4 ?

Balance the chemical equation given below, and determine the number of moles of iodine that reacts with 30.0 g of aluminum. ________ Al(s) + ________ I2(s) → ________ Al2I6(s)

Lithium and nitrogen react to produce lithium nitride: 6Li(s) + N2(g) → 2Li3N(s) How many moles of lithium nitride are produced when 0.450 mol of lithium react in this fashion?

Lithium and nitrogen react to produce lithium nitride: 6Li(s) + N2(g) → 2Li3N(s) How many moles of N2 are needed to react with 0.500 mol of lithium?

What is the oxidation number of the chromium atom in K2CrO4 ?

How many millilitres of 0.132 mol L-1 HClO4 solution are needed to neutralize 50.00 mL of 0.0789 mol L-1 NaOH?

What is the oxidation number change for the bromine atom in the following unbalanced reduction half-reaction: Br O3- (aq) + H+(aq) → Br-(aq) + H2O(l)

What are the coefficients in front of NO3-(aq) and Cu(s) when the following redox equation is balanced in an acidic solution? ___ NO3-(aq) + ___ Cu(s) → ___ NO(g) + ___ Cu2+(aq) ?

What is the oxidation number of the oxygen atom in Na2O2 ?

How many grams of calcium chloride are needed to produce 1.50 g of potassium chloride? CaCl2(aq) + K2CO3(aq) → 2KCl(aq) + CaCO3(aq)

How many moles of BCl3 are needed to produce 10.0 g of HCl(aq) in the following reaction? BCl3(g) + 3H2O(l) → 3HCl(aq) + B(OH) 3(aq)

What is the molarity of a NaOH solution if 28.2 mL of a 0.355 mol L-1 H2SO4 solution is required to neutralize a 25.0 mL sample of the NaOH solution?

Automotive air bags inflate when sodium azide decomposes explosively to its constituent elements: 2NaN3(s) → 2Na(s) + 3N2(g) How many grams of sodium azide are required to produce 33.0 g of nitrogen?

How many moles of CuO can be produced from 0.900 mol of Cu2O in the following reaction? 2Cu2O(s) + O2(g) → 4CuO(s)

Lithium and nitrogen react in a combination reaction to produce lithium nitride: 6Li(s) + N2(g) → 2Li3N(s) How many moles of lithium are needed to produce 0.60 mol of Li3N when the reaction is carried out in the presence of excess nitrogen?

Balance the chemical equation given below, and determine the number of grams of MgO needed to produce 10.0 g of Fe2O3. ________ MgO(s) + ________ Fe(s) → ________ Fe2O3(s) + ________ Mg(s)

Automotive air bags inflate when sodium azide decomposes explosively to its constituent elements: 2NaN3(s) → 2Na(s) + 3N2(g) How many moles of N2 are produced by the decomposition of 2.88 mol of sodium azide?

Magnesium burns in air with a dazzling brilliance to produce magnesium oxide: 2Mg(s) + O2(g) → 2MgO(s) When 4.00 g of magnesium burns, what is the theoretical yield of magnesium oxide?

Dinitrogen monoxide gas decomposes to form nitrogen gas and oxygen gas. How many grams of oxygen are formed when 10.0 g of dinitrogen monoxide decomposes?

Magnesium burns in air with a dazzling brilliance to produce magnesium oxide: 2Mg(s) + O2(g) → 2MgO(s) How many moles of O2 are consumed when 0.770 mol of magnesium burns?

What is the oxidation number of the sulfur atom in K₂SO₄?

Balance the chemical equation given below, and determine the number of moles of iodine that reacts with 30.0 g of aluminum. Al(s) + I₂(s) → Al₂I₆(s)

Lithium and nitrogen react to produce lithium nitride: 6Li(s) + N₂(g) → 2Li₃N(s) How many moles of lithium nitride are produced when 0.450 mol of lithium react in this fashion?

Lithium and nitrogen react to produce lithium nitride: 6Li(s) + N₂(g) → 2Li₃N(s) How many moles of N₂ are needed to react with 0.500 mol of lithium?

What is the oxidation number of the chromium atom in K₂CrO₄?

How many millilitres of 0.132 mol L^-1 HClO₄ solution are needed to neutralize 50.00 mL of 0.0789 mol L^-1 NaOH?

What is the oxidation number change for the bromine atom in the following unbalanced reduction half-reaction: BrO₃^-(aq) + H⁺(aq) → Br^-(aq) + H₂O(l)

What are the coefficients in front of NO₃^-(aq) and Cu(s) when the following redox equation is balanced in an acidic solution? _ NO₃^-(aq) + _ Cu(s) → _ NO(g) + _ Cu²⁺(aq) ?

What is the oxidation number of the oxygen atom in Na₂O₂?

How many grams of calcium chloride are needed to produce 1.50 g of potassium chloride? CaCl₂(aq) + K₂CO₃(aq) → 2KCl(aq) + CaCO₃(aq)

How many moles of BCl₃ are needed to produce 10.0 g of HCl(aq) in the following reaction? BCl₃(g) + 3H₂O(l) → 3HCl(aq) + B(OH) ₃(aq)

What is the molarity of a NaOH solution if 28.2 mL of a 0.355 mol L^-1 H₂SO₄ solution is required to neutralize a 25.0 mL sample of the NaOH solution?

Automotive air bags inflate when sodium azide decomposes explosively to its constituent elements: 2NaN₃(s) → 2Na(s) + 3N₂(g) How many grams of sodium azide are required to produce 33.0 g of nitrogen?

How many moles of CuO can be produced from 0.900 mol of Cu₂O in the following reaction? 2Cu₂O(s) + O₂(g) → 4CuO(s)

Lithium and nitrogen react in a combination reaction to produce lithium nitride: 6Li(s) + N₂(g) → 2Li₃N(s) How many moles of lithium are needed to produce 0.60 mol of Li₃N when the reaction is carried out in the presence of excess nitrogen?

Balance the chemical equation given below, and determine the number of grams of MgO needed to produce 10.0 g of Fe₂O₃. MgO(s) + Fe(s) → Fe₂O₃(s) + Mg(s)

Automotive air bags inflate when sodium azide decomposes explosively to its constituent elements: 2NaN₃(s) → 2Na(s) + 3N₂(g) How many moles of N₂ are produced by the decomposition of 2.88 mol of sodium azide?

Magnesium burns in air with a dazzling brilliance to produce magnesium oxide: 2Mg(s) + O₂(g) → 2MgO(s) When 4.00 g of magnesium burns, what is the theoretical yield of magnesium oxide?

Magnesium burns in air with a dazzling brilliance to produce magnesium oxide: 2Mg(s) + O₂(g) → 2MgO(s) How many moles of O₂ are consumed when 0.770 mol of magnesium burns?