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Chemical Reactions, Solutions, and Gas Laws
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Chemical Reactions, Solutions, and Gas Laws
Chemical Reactions, Solutions, and Gas Laws
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1
Question
How does a chemical equation represent a reaction between substances?
Page 1
Answer
It places reactant formulas on the left and product formulas on the right of an arrow, which means “produces.”
2
Question
How does a balanced equation reflect conservation of atoms?
Page 1
Answer
It has an equal number of atoms of each element on both sides of the arrow.
3
Question
What information do coefficients provide in a chemical equation?
Page 1
Answer
They indicate the relative numbers of molecules of each kind involved in the reaction.
4
Question
Which physical state does each symbol indicate in a chemical equation?
Page 1
Answer
(g) gas; (l) liquid; (s) solid; (aq) dissolved in aqueous solution.
5
Question
How does a combination reaction differ from a decomposition reaction?
Page 1
Answer
A combination reaction joins two or more substances to form one product. A decomposition reaction starts with one substance and forms two or more substances.
6
Question
Which products form when magnesium reacts with oxygen?
Page 1
Answer
Magnesium oxide forms: 2 Mg(s) + O₂(g) → 2 MgO(s).
7
Question
What products form when calcium carbonate is heated?
Page 1
Answer
Calcium oxide and carbon dioxide form: CaCO₃(s) → CaO(s) + CO₂(g).
8
Question
Why must a chemical equation be balanced?
Page 1
Answer
Atoms are neither created nor destroyed in a reaction, so each element must have equal atom counts on both sides.
9
Question
How should coefficients be selected when balancing equations?
Page 2
Answer
Choose coefficients that give equal numbers of each type of atom on both sides, using the smallest possible whole numbers for most purposes.
10
Question
Which coefficient balances oxygen in methane combustion?
Page 2
Answer
CH₄ + 2 O₂ → CO₂ + 2 H₂O; the coefficient of O₂ is 2.
11
Question
How do you convert a mass of a substance into moles?
Page 2
Answer
Divide the given mass by the substance’s molar mass: moles = mass ÷ molar mass.
12
Question
How many moles are in 5.380 g of glucose using the given molar mass?
Page 2
Answer
Using 180.0 g/mol, 5.380 g corresponds to 0.02989 mol of glucose.
13
Question
How many moles of carbon dioxide form from 3 mol of butane?
Page 2
Answer
12 mol CO₂ form, using the balanced ratio 2 mol C₄H₁₀ : 8 mol CO₂.
14
Question
How many moles of octane are present in a 1 g sample?
Page 3
Answer
Using a molar mass of 114 g/mol, 1 g of C₈H₁₈ is 0.00878 mol.
15
Question
Which balanced equation describes complete combustion of octane?
Page 3
Answer
2 C₈H₁₈ + 25 O₂ → 16 CO₂ + 18 H₂O.
16
Question
What is an aqueous solution?
Page 3
Answer
A solution in which water is the dissolving medium.
17
Question
How do solvent and solute differ in a solution?
Page 3
Answer
The solvent is usually the component present in the greatest quantity. The other substances are solutes dissolved in it.
18
Question
In salt water, which substance is the solvent and which is the solute?
Page 3
Answer
Water is the solvent, and sodium chloride is the solute.
19
Question
How does an electrolyte differ from a nonelectrolyte in aqueous solution?
Page 3
Answer
An electrolyte’s aqueous solution contains ions. A nonelectrolyte does not form ions in solution.
20
Question
Why is sodium chloride classified as an electrolyte but sucrose as a nonelectrolyte?
Page 3
Answer
NaCl is an ionic compound whose aqueous solution contains ions. C₁₂H₂₂O₁₁ is a molecular compound that does not form ions in solution.
21
Question
When does a reaction qualify as a precipitation reaction?
Page 3
Answer
When it forms an insoluble product in solution.
22
Question
What is a precipitate in a solution reaction?
Page 3
Answer
An insoluble solid formed by a reaction in solution.
23
Question
Why can oppositely charged ions form a precipitate?
Page 3
Answer
They can attract strongly enough to form an insoluble ionic solid.
24
Question
How is solubility defined at a given temperature?
Page 4
Answer
It is the amount of a substance that can dissolve in a given quantity of solvent at that temperature.
25
Question
How do alkali-metal carbonates behave in water under the stated guidelines?
Page 4
Answer
They are soluble, although most carbonates are insoluble.
26
Question
Why is sodium carbonate soluble in water?
Page 4
Answer
Most carbonates are insoluble, but carbonates of alkali metal cations such as sodium are an exception and are soluble.
27
Question
Why is lead sulfate classified as insoluble in water?
Page 4
Answer
Most sulfates are soluble, but sulfate compounds of Pb²⁺ are an exception; therefore PbSO₄ is insoluble.
28
Question
Which precipitate forms when aqueous barium chloride and potassium sulfate are mixed?
Page 5
Answer
Barium sulfate, BaSO₄, precipitates; potassium chloride remains soluble.
29
Question
Which balanced equation represents barium chloride reacting with potassium sulfate?
Page 5
Answer
BaCl₂(aq) + K₂SO₄(aq) → BaSO₄(s) + 2 KCl(aq).
30
Question
How are acids described by their behavior in aqueous solution?
Page 5
Answer
They ionize in aqueous solution to form H⁺ ions and are often called proton donors.