HNS Chem Exam Study Guide

What is true about the mole?

• it measures the amount of a substance

• 6.02 × 10²³ representative particles of a substance

• it is also called Avagadro’s number

What is the representative particle in nitrogen dioxide, NO₂?

molecule (NM + NM)

One mole of carbon contains 6.02 × 10²³ atoms of carbon and it weighs ____ grams.

12.0 g

What are the coefficients that balance the following equation? H₂ + Cl₂ → HCl

1, 1, 2

What are the coefficients that balance the following equation? Al + H₂SO₄ → Al₂(SO₄)₃ + H₂

2, 3, 1, 3

Calculate the molar mass of glucose, C₆H₁₂O₆ and use this number to solve the next problem.

180 g/mol

What is the mass in grams of 3.2 moles of glucose, C₆H₁₂O₆?

576 g

What is the correct skeleton equation for the following chemical reaction? Solid sulfur burns in the presence of oxygen gas to produce sulfur dioxide gas.

S(s) + O₂(g) → SO₂(g)

What happens when a chemical reaction occurs?

atoms are arranged to make new products

What is the correct balanced equation for the following chemical reaction? Propane gas, C₃H_8, burns in the presence of oxygen gas to form carbon dioxide gas and water vapor.

C₃H₈(g) + 5O₂ → 3CO₂(g) + 4H₂O(g)

2Fe + 3S → Fe₂S₃

combination or synthesis

MgO → Mg + O₂

decomposition

Zn + Cu(NO₃)₂ → Cu + Zn(NO₃)₂

single replacement

AgNO₃ + NaCl → AgCl + NaNO₃

double replacement

CH₄ + 2O₂ → CO₂ + H₂O

combustion

Predict the products of the skeleton equation when solid zinc reacts with aqueous copper chloride. Zn(s) + CuCl₂(aq) → ?

Cu(s) + ZnCl₂(aq)

Predict the products of the skeleton equation when solid dinitrogen trioxide decomposes to form gases.

N₂(g) + O₂(g)

The Law of Conservation of Mass is obeyed when:

the mass of the reactants is equal to the mass of the products

#19 on Study Guide

kinetic theory of matter

states that all matter consists of tiny particles that are in constant motion

How does an airbag help prevent injury in a car crash?

the compression of gas molecules absorbs the impact

What are the units for measuring pressure?

• pascals

• mm Hg

• atmospheres

What are the methods to increase the pressure inside a container of gas, if all other conditions are held constant?

• add more gas particles

• add heat to the container

• decreasing the volume of the container

A balloon contains 120.0L of helium gas at 103 kPa. What is the volume of the helium gas when the balloon rises to an altitude where the pressure is only 48.0 kPa? What Law will use to solve the problem?

Boyle’s Law

What is the new volume of the helium gas in the problem above?

257.5 L

The above answer makes sense because as the pressure on the balloon decreases, we would expect what?

the ballon to expand to a larger volume

A balloon inflated in a room at 20°C has a volume of 4.0 L. The balloon is then heated to a temperature of 35°C. What is the new volume if the pressure remains constant? What Law will you use to solve the problem?

Charles’s Law

What is the new volume of the balloon in the problem above?

4.2 L

The above answer makes sense because as the temperature of the gas increases, we would expect what?

the balloon to expand to a larger volume

If salt is dissolved in water, water serves as the:

solvent

What time of bond is formed between the oxygen atom and each of the hydrogen atoms in a single water molecule?

polar covalent bond

What type of bond is formed between the hydrogen atoms of one water molecule and the oxygen atom of a different water molecule?

hydrogen bond

Hydrogen bonding between water molecule is responsible for which of these unique properties of H₂O?

• high surface tension

• low vapor pressure

• solid ice is less dense than liquid water

What types of compounds dissolve in water?

ionic and polar covalent

What expression sums up the dissolving of polar or nonpolar substances?

“Like dissolves Like”

What operations ususally makes a solid substance dissolve faster in a solvent?

• agitation or stirring

• increasing the temperature

• increasing the surface area of the substance

The amount of solute that dissolves in a given quantity of a solvent at a specified temperature and pressure to produce a saturated solution is:

• a substance's solubility

• expressed in grams of solute per 100 grams of solvent

• usually increased for solids as temperature increases

Thermal pollution is the dumping of heated water into lakes and rivers, lowering dissolved O₂ levels, which kills aquatic life. What property of solutions is involved in this scenario?

gases are more soluble in cold water than hot water

Carbonated beverages bottled under high pressure become flat when left uncapped. What property of solutions is involved?

a decrease in the pressure of a gas above a solution decreases the solubility of the gas

#40 on Study Guide

What is the molarity of 500 mL of solution in which 2.0 moles of sodium bromide is dissolved?

4.0 M

What is true about heat energy?

• it is energy that transfers between objects because of a temperature difference between them

• if two objects are in contact, heat will continue to flow until the temperature of both objects is the same

• heat is represented by the letter q in thermochemistry

• heat always flows from a warmer object to a cooler object

Hot melted wax solidifies as it cools. What process is involved?

exothermic

Ammonium nitrate (the system) dissolves when a cold pack is squeezed, making the cold pack very cold. What process is involved?

endothermic

#45 on Study Guide

True or False: A 2 kilogram iron frying pan has a greater heat capacity than a 2 gram iron nail.

true

True or False: A 20 kilogram iron sewer cover has a greater heat capacity than a 20 kg puddle of water.

false

In which substance does it take the largest amount of heat energy to raise the temperature of 1 gram of that substance 1°C? (refer to Table 17.1)

water

A 26.3 g sample of an unknown substance was heated from 22.1°C to 34°C. In the process, the substance absorbed 74 Joules of energy. What is the specific heat of the substance?

0.24 J/(g x C)

What is the identity of the substance from the above question?

silver

A small piece of unknown metal was heated and placed in a foam cup calorimeter containing 50.0 mL of water at 20.0°C. The water reaches a maximum temperature of 25.8 °C. How many kilojoules of heat were released by the metal?

-1.2 kJ

A potato chip is placed in a bomb calorimeter containing 250 mL of water at 20.0°C. The water reaches a maximum temperature of 55.0°C. How many calories of heat were released by the chip?

-8750 calories

How many food calories are in the potato chip in the previous question? (round to one decimal place)

9 calories

In the following thermochemical equation, CaO(s) + H₂O(l) → Ca(OH)₂(s) + 65.2 kJ

65.2 kJ of heat are produced by the reaction of CaO and H₂O

#55 on Study Guide

What is the name of the following acid? H₂CO₃

carbonic acid

What is the name of the following acid? HF

hydrofluoric acid

What is the name of the following acid? HClO₂

chlorous acid

What is the formula for the following acid? sulfurous acid

H₂SO₃

What is the formula for the following acid? nitric acid

HNO₃

What is the name of the following base? Fe(OH)₂

iron (II) hydroxide

What is the formula of the following base? zinc hydroxide

Zn(OH)₂

What household items would be an example of an acidic substance?

• lemons/oranges

• Coca-Cola soda

• car battery

Why is pure water neutral on the pH scale?

it contains equal concentrations of H₃O⁺ and OH^- ions

What are examples of an Arrhenius acid?

• HCl

• HNO₃

• H₂SO₄

True or False: Milk of Magnesia, Mg(OH)₂, can be taken internally because Mg(OH)₂ is very soluble in water and makes a concentrated, strongly basic solution.

false

#67 on Study Guide

#68 on Study Guide

What are properties of acids?

• taste sour

• ionizes to form strong or weak electrolytes

• changes color of acid/base indicators

• reacts with metals → H₂(g)

Given the following reaction of an acid and a metal, what is typically the product of this type of reaction? 2HCl(aq) + Mg(s) → MgCl₂(aq) + H₂(g)

H₂

When ammonia is added to water, the ammonium and hydroxide ions are produced and the reaction is reversible. What is the acid in the forward reaction?

H₂O

What is the conjugate base in the reverse reaction?

OH^-

What is a conjugate acid-base pair from this reaction?

NH₃ & NH₄⁺

When HNO₃ is added to water, the hydronium ion and the nitrate ion are produced and the reaction is reversible. What is the acid in the forward reaction?

HNO₃

What is the conjugate acid in the reverse reaction?

H₃O⁺

What is a conjugate acid-base pair from this reaction?

H₂O & H₃O⁺

What is the amphoteric substance in the above two reactions involving NH₃ and water, and HNO₃ and water?

H₂O

What is the formula for the conjugate base of HSO₃^-?

SO₃^2-

What is the formula for the conjugate acid of HS^-?

H₂S

If the [H+] of a solution is greater than 1 × 10^-7, the solution will be

acidic

#81-82 on Study Guide

What is the [OH-] of a solution if the [H+] is 1.0 × 10^-3 M?

[OH-] = 1 × 10^-11 M

A difference of one unit on the pH scale corresponds to a ____ fold change in the concentration of H₃O⁺ ions

10

What is the pH of a solution whose [H+] = 0.0001 M?

4

A solution has an [H+] of 1.0 × 10^-6 M. Determine the pH and the pOH. Is it acidic, basic or neutral?

the pH is: 6

the pOH is: 8

the solution is: acidic

A solution has an [H+] of 2.1 × 10^-11 M. Determine the pH and the pOH. Is it acidic, basic or neutral? Round to one decimal place.

the pH is: 10.7

the pOH is: 3.3

the solution is: basic

A solution has a pH of 12. What is the [H+] of the solution?

[H+] = 1 × 10^-12 M

A solution has a pH of 4.7 What is the [H+]?

[H+] = 2 × 10^-5 M

Determine the pH of a solution with an [OH-] = 3.7 × 10^-10 M

4.6

Determine the pH of a solution with an [OH-] = 5.5 × 10^-8 M

6.7

What happens when you combine an acid and a base?

a neutralization reaction

When carbon dioxide in the atmosphere combines with water in the oceans, carbonic acid forms. The resulting ecological problem is called ocean

acidification