Unit 4 Chemistry Q&A's

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All unit 4 Chemistry questions and answers; checkpoints, workbooks, and exams.

Which of the following is the basic procedure for stoichiometry?

write a balanced equation, define the mole ratios, convert units into moles, apply the mole ratios, convert into the desired units

In doing stoichiometric problems, you must begin with ______.

a balanced equation

The activity series enables the chemist to determine ______.

which metals replace others in displacement reactions

Which of the following metals in very unreactive?

platinum

The shiny parts of many cars are steel on which chromium has been electroplated. Will the chromium react with water in the atmosphere?

no

Aluminum metal is placed in an aqueous solution of potassium chloride. Will there be a reaction?

no

In a single-replacement reaction, one metal will replace another in an ionic compound only if the first metal is ______.

higher in the activity series

How many molecules of water are formed from four molecules of ammonia when it is reacted with excess oxygen?

six

If the given and unknown values are both in moles in a stoichiometric problem, what do you have to do to obtain the unknown?

multiply the given by the mole ratio obtained from the balanced equation

Which of the following is always a necessity in a stoichiometric problem?

a balanced equation

Reaction stoichiometry involves mass relationships between products and reactants in a chemical reaction, which yields a _____.

mole ratio

How many moles of oxygen atoms would it take to react completely with 4 moles of zinc atoms?

two

A determination of the masses and number of moles of sulfur and oxygen in the compound sulfur dioxide would be studied in ______.

composition stoichiometry

To balance a chemical equation, it may be necessary to adjust the _____.

coefficients

A chemical equation is balanced when the _____.

same number of each kind of atom appears in the reactants and in the products

A balanced chemical equation allows one to determine the _____.

mole ratio of any two substances in the reaction

Each of the four types of reaction stoichiometry problems requires using a ____.

mole ratio

When the formula equation, Fe3O4 + Al => Al2O3 + Fe, is correctly balanced, the coefficient of Fe is the number _____.

9

For the reaction represented by the equation 2H2 + O2 => 2H2O, how many grams of water are produced from 6.00 mol of hydrogen?

108 g

Predict what happens when calcium metal is added to a solution of magnesium chloride.

calcium chloride forms

Predict what happens when lead is added to nitric acid.

hydrogen is released

In order to calculate the mass of a product of an ideal reaction, you must first know _____.

the balanced chemical equation and mass or amount of any other reactant or product

Which of the following is NOT a step in solving quantitative problems in chemistry?

covert all solid measures to volumes

In the reaction, 2H2 + O2 => 2H2O, the mole ratio of hydrogen to water is ______.

1:1

How many moles of water is 54 grams? (atomic mass for H is 1.01, for oxygen is 15.99)

3.0 moles

Given the ideal equation, CH4 + 2O2 => CO2 + 2H2O, how many grams of carbon dioxide will be produced from 8.0 grams of methane, CH4?

22 grams

An ideal reaction is one in which ______.

all reactants are converted into products

What is the mass of 6.022 x 1023 molecules of water?

18.01 grams

Before the mole ratio can be applied in stoichiometric problems, _____.

all units must be converted into moles

How many moles of oxygen gas are needed to react with 10.0 mol of ammonia, according to the equation, 4NH3 + 7O2 => 4NO2 + 6H2O ?

17.5 moles

If 0.500 moles of sodium azide decomposes into sodium and nitrogen according to the following equation, 2NaN3 => 2Na + 3N2, what is the mass of nitrogen gas that would be produced?

21.0 g

What is the mass, in grams, of ammonium perchlorate required to react with 35.5 moles of aluminum, according to the following reaction, 3Al + 3NH4ClO4 => Al2O3 + AlCl3 + 3NO +6H2O ?

4150 grams

How many moles of hydrogen gas are produced if 454 g of methane are reacted according to the reaction, CH4 + H2O => 3H2 + CO?

85.1 moles

How many grams of carbon dioxide are produced when 175 g of propane are combusted with oxygen, according to the reaction, C3H8 + 5O2 => 3CO2 + 4H2O?

524 g

In the reaction represented by the equation N2 + 3H2 => 2NH3, what is the mole ratio of hydrogen to ammonia?

3:2

In the reaction represented by the equation C + 2H2 => CH4, what is the mole ratio of hydrogen to methane?

2:1

In the equation 2KClO3 => 2KCl + 3O2, how many moles of oxygen are produced when 3.0 mol of KClO3 decompose completely?

4.5

A car air bag requires 70. L, or 3.125 moles, of nitrogen gas to inflate properly. The following equation represents the production of nitrogen gas:
2NaN3(s) =>2Na(s) + 3N2(g)

How many grams of NaN3 must be used to generate the amount of N2 necessary to properly inflate the air bag?

[atomic masses: Na = 22.990, N = 14.007; molar volume of any gas = 22.4 liters]

135 grams

For the reaction represented by the equation Pb(NO3)2 + 2KI => PbI2 + 2KNO3, how many moles of lead(II) iodide are produced from 300. g of potassium iodide and an excess of Pb(NO3)2?

0.904 mol

In the reaction represented by the equation 2Al2O3 => 4Al + 3O2, what is the mole ratio of aluminum to oxygen?

4:3

For the reaction represented by the equation C + 2H2 => CH4, how many moles of hydrogen are required to produce 10 mol of methane, CH 4?

20 mol

What mass in grams of hydrogen gas is produced if 20.0 mol of Zn are added to excess hydrochloric acid according to the equation Zn(s) +2HCl(aq) => ZnCl2(aq) + H2(g)?

40.4 g

For the reaction represented by the equation SO3 + H2O => H2SO4, how many grams of sulfuric acid can be produced from 200. g of sulfur trioxide and 100. g of water? (O = 16.0 amu; S = 32.1 amu; H =1.01 amu)

245 g

For the reaction represented by the equation 2H2 + O2 => 2H2O, how many moles of water can be produced from 6.0 mol of oxygen?

12 mol

Barring errors, actual yields are always _____.

less than or equal to theoretical yields

Percentage yield compares _____.

actual to theoretical yields

In examining a compound, it is found that it is made only of hydrogen and oxygen and that the percentage composition of hydrogen is 11.1% and of oxygen 88.9%. What is the empirical formula of the compound?

HO

The difference between a limiting and an excess reactant is _____.

the amount available of the reactant

In which of the following types of reaction are there no limiting or excess reactants?

decomposition

In the automobile engine, octane is combusted to form carbon dioxide and water. Which of the following is a major reason why the actual yield of carbon dioxide is smaller than the theoretical yield?

formation of carbon monoxide

To derive percent yield, you divide the actual yield by the theoretical yield and _____.

multiply by 100 and put a percent sign after it

The excess reactant is the one whose ____.

actual amount is greater that the stoichiometric proportion required

The limiting reactant is the one which _____.

determines the maximum amount of product formed

If the theoretical yield of a reaction is 200 grams, and the actual yield is 180 grams, the percentage yield is _____.

90%

In the reaction of magnesium hydroxide with hydrochloric acid, Mg(OH)2 + HCl => MgCl2 + 2H2O, there is 0.5 mol of magnesium hydroxide available to react with 0.25 mol of hydrochloric acid. Which is the limiting reactant?

hydrochloric acid

What is the mass of copper oxide, CuO, that reacts with 35.0 grams of ammonia gas, NH3, according to the following equation? 2NH3 + 3CuO => N2 + 3Cu + 3H2O

246 grams CuO

What is the percent yield of benzene, when 0.418 grams of acetylene produce 0.374 grams of benzene?

89.5%

Joseph Priestley is credited with the discovery of oxygen. He produced O2 by heating mercury (II) oxide, HgO, to decompose it into its elements. How many moles of oxygen could Priestley have produced if he had decomposed 517.84 grams of mercury (II) oxide? The molar mass of mercury is 200.59 grams; and that of oxygen is 15.999 grams.

1.1954 moles

Ideal gases are those that _____.

conform to the formula, PV = nRT

A state of matter in which there is little bonding between particles is a _____.

gas

Kinetic molecular theory describes the relationship of temperature, pressure, and volume in _____.

gases

In a gas, the higher the temperature, _____.

the faster its particles are moving

The tendency of pressurized gases to escape through a hole in the container is called _____.

effusion

If two gases have no barrier between them, their particles will ______.

diffuse

One factor that causes gases to vary from ideal behavior is ______.

polar particles

According to kinetic molecular theory, the temperature of a gas is related to its ______.

average kinetic energy of its particles

Which of the following statements violates the assumptions of the kinetic molecular theory?

gas particles are attracted to each other

The term fluids describes ______.

gases and liquids

In many gases, the particles are of similar size. In such gases, the temperature of the gas is most closely related to _____.

the square root of the average velocity of the particles

A real gas ____.

does not obey all the assumptions of the kinetic molecular theory

The kinetic-molecular theory explains the behavior of _____.

solids, liquids, and gases

According to the kinetic-molecular theory, gases condense into liquids because of ______.

forces between molecules

What happens to the volume of a gas during compression?

the volume decreases

According to the kinetic-molecular theory, which is the most significant difference between gases and liquids?

the distance between the particles

According to the kinetic-molecular theory, how does a gas expand?

its particles move greater distances

The kinetic-molecular theory explains the properties of solids, liquids, and gases in terms of the energy of the particles and ______.

the forces between the particles

Two gases with unequal molar masses are injected into opposite ends of a long tube at the same time and allowed to diffuse toward the center. They should begin to mix ______.

closer to the end that holds the heavier gas

Which substance has the lowest density?

H2O (g)

By which process do gases take the shape of their container?

expansion

Diffusion between two gases occurs most rapidly if the gases are at _____.

high temperature and the particles are small

Solids can be either crystalline or ______.

amorphous

Which of the following correctly describes condensation?

energy of the system is lost until kinetic energy of the particles does not dramatically exceed intermolecular forces

The smallest volume in which the geometry of a crystalline structure is evident is the _____.

unit cell

A fluid is a material in which particles can pass by each other freely. Fluids are either ______.

liquids or gases

The final state of a diffused liquid is _____.

an even-spaced distribution of all components

Which of the following is NOT a common property in liquids?

compressibility

The reason for surface tension in a liquid is ______.

the energy content of surface molecules is greater

The force that draws liquid upward in capillary action is _____.

the attraction between liquid and solid molecules

Once the molecules of a liquid are captured into a solid crystal structure ______.

their potential energy is so much lower that it requires a good deal of energy to overcome the lattice energy

One reason evaporation is a crucial process in nature is that ______.

it is a cooling mechanism for land animals

Surface tension makes ______.

water droplets bead up into spherical shapes

Compared to liquids and gases, diffusion into solids is ______.

much slower

The lower plateau on a time-temperature graph indicates the ______.

melting point

Ionic compounds melt at high temperatures because ______.

the strength of their ionic bonds is harder to overcome

A pyramidal cell results in a ______.

trigonal crystal

A good example of a covalent molecular crystal is ______.

ice

Plastics and glass are examples of _____.

amorphous solids

Crystalline solids ______.

have a definite melting point

Quartz and diamonds are _______.

covalent network crystals

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