Chemistry Answers

Question 14

In the above reaction in question 13, 2 moles of Mg and 5 moles of O₂ are allowed to react.

Which reagent is the limiting reagent?

a. Mg

b. O₂

c. MgO

d. There is no limiting reagent

e. Both Mg and O₂ are limiting reagents

Question 15

What is the maximum number of moles of MgO that can be formed?

a. 1 mol

b. 2 mol

c. 5 mol

d. 40.3 mol

e. 80.6 mol

Question 16

Calculate how many moles of the excess reagent remain unreacted.

a. 1 mol

b. 2 mol

c. 4 mol

d. 5 mol

e. No excess reagent remains unreacted

Question 17

Suppose that the actual moles of MgO produced was 0.5 mol, what is the percentage yield of MgO?

a. 0.62%

b. 1.2%

c. 10%

d. 25%

e. 50%

Question 18

The value of a solution concentration unit that may change with temperature is

a. molarity.

b. mole fraction.

c. molality.

d. mole percentage.

e. weight percentage.

Question 9

Calculate the number of moles of NH₃ present in 100 g of NH₃

a. 0.170 mol

b. 5.87 mol

c. 17.0 mol

d. 100 mol

e. 1703 mol

Question 10

Calculate the mass percentage of hydrogen in methane, CH₄

a. 0.062 %

b. 0.251 %

c. 6.28 %

d. 12.6 %

e. 25.1 %

 Question 11

A compound which contains 0.0130 mol C, 0.390 mol H and 0.065 mol O. What is the empirical formula for this compound?

a. CHO

b. CH₅O₂

c. CH₃₀O₅

d. CH₃₉O₆

e. C₂H₆₀O₁₀

Question 12

What is the empirical formula for a compound that contains 17.34 % hydrogen and 82.66 % carbon by mass?

a. CH

b. CH₂

c. CH₃

d. C₂H₅

e. C₅H

 Question 13

Consider the following information to answer questions 13-17 below:

The unbalanced reaction of magnesium with oxygen is:

Mg + O₂ → MgO

 The correct balanced reaction is:

a. Mg₂ + O₂ → 2MgO

b. 2Mg + ½ O₂ → Mg₂O

c. 2Mg + O₂ → 2MgO  

d. Mg + O₂ → MgO₂

e. None of the above

Question 5

Given then the following reactions below, which one involves neither oxidation nor reduction?

a. Cl₂ + H₂O → HCl + HOCl

b. 2Na + 2H₂O → 2NaOH + H₂

c. 3NO₂ + H₂O → 2HNO₃ + NO

d. POCl₃ + 3H₂O → H₃PO₄ + 3HCl

e. 2H₂O → 2H₂ + O₂

Question 6

Calculate the oxidation number of phosphorus in KH₂PO₄?

a. -6

b. -2

c. 0

d. +5

e. +6

 Question 7

Reactions which cannot occur spontaneously are called:

a. exothermic

b. endothermic

c. all reactions can occur spontaneously

d. no reactions can occur spontaneously

e. both [a] and [b]

Question 8

Calculate the number of moles of hydrogen atoms in one mole of (NH₄)₂SO₄.

a. 1

b. 2

c. 4

d. 8

e. 15

Question 1

By applying the solubility guidelines, state which of the following compounds will precipitate in water?

a. Cobalt (II) hydroxide.

b. Sodium nitrate.

c. Ammonium phosphate.

d. Potassium Chloride.

e. None of the above.   

Question 2

Consider an acid-base reaction when Nitric acid is added to copper(II) hydroxide. What is the net ionic equation for this reaction?

a. H⁺(aq) + OH^-(aq) → H₂O(l)

b. 2H⁺(aq) + Cu(OH)₂(s) → Cu²⁺(aq) + 2H₂O(l)

c. 2HNO₃(aq) +Cu(OH)₂(s) → Cu(NO₃)₂(s) + 2H₂O(l)

d. 2H⁺(aq) + 2NO₃^-(aq) + Cu²⁺(aq) + 2OH^-(aq) → Cu(NO₃)₂(s) + 2H₂O(l)

e. 2H⁺(aq) + 2NO₃^-(aq) + Cu²⁺(aq) + 2OH^-(aq) → Cu²⁺(aq) + 2NO₃^-(aq) + 2H₂O(l)

 Question 3

In a certain reaction, element X was converted to X^2-. In the reaction, X acts as

a. a precipitating agent

b. an acid

c. a base

d. a reducing agent

e. an oxidizing agent

 Question 4

Identify the type of reagent that is required to convert N₂H₄ to N₂?

a. acid

b. base

c. reducing agent

d. oxidizing agent

e. precipitating agent

1. If 1.3 L of 3.0M potassium hydroxide completely neutralizes 0.7 L of carbonic acid

(H2CO3), what is the concentration of the carbonic acid? 2KOH+H,CO, K,CO,+2H₂O

2. How many moles of HCl are present in 0.07 L of 6 M HCI? 3. I add 7 mL of 2 M NaOH to 50 mL of water. What is the new concentration?

Rates of Reactions-Le Chatlier's Principle

2KOH+H₂CO,→K.CO,+2H2O overall energy of reaction (AH)=-683.84 kJ/mol 1. Describe 2 ways you could increase the amount of products of this reaction at

equilibrium. 2. Describe 2 ways you could increase the amount of reactants of the reaction at

equilibrium.

A student collects 25 mL of gas at 96 kPa. What volume would this gas

        occupy at 101.325 kPa. There’s no change in temperature or mass.

How many liters of 0.55 M HCl is required to neutralize 1.10 g of sodium carbonate (Na2CO3)? (molar mass of Na2CO3 = 105.99 g/mol)

2HCl + Na2CO3 → 2NaCl + H2CO3

1.078 g sample of a compound containing only carbon, hydrogen, and oxygen is burned in an excess of dioxygen, producing 2.451 g CO2 and 1.003 g H2O.

ulfur trioxide (SO3) is produced from the oxidation of SO2 as follows:

2 SO2 + O2 → 2 SO3

A 23-g sample of SO2 gives 18 g of SO3. Calculate the percent yield of sulfur trioxide, SO3.

A. 10 %

Automotive airbags inflate when sodium azide decomposes explosively to its constituent elements. How many moles of NA are produced by the decomposition of 1.75 mol of sodium azide