Lesson 14 - Quiz #7

Which set of coefficients balance the following chemical equation?

1, 3, 2

How much energy is released upon the formation of the bonds within 1 mole of hydrazine, N2H4? (Bond energies: H—N = 389 kJ/mol; N—N = 159 kJ/mol)

1,715 kJ

When the hydroxide ion concentration equals 1 10-5 moles per liter, what is the pH of the solution?

9

What correlation might you expect between an element's electronegativity and its ability to behave as an oxidizing agent? How about its ability to behave as a reducing agent?

Atoms with great electronegativity tend to behave as strong oxidizing agents and weak reducing agents.

Which of the following shows elements in order of increasing atomic size (Cl, atomic number 17; K, atomic number 19; Br, atomic number 35; Rb, atomic number 37)?

Cl < Br < K < Rb

Magnesium ions carry a 2+ charge and chloride ions carry a 1- charge. What is the chemical formula for the ionic compound magnesium chloride?

MgCl2

Are there hydrogen bonds between water molecules in the liquid phase?

No; otherwise, the water molecules would not be able to tumble over one another.

Why doesn't the sodium atom gain seven electrons so that its third shell becomes the filled outermost shell?

Sodium's nuclear charge is not strong enough to hold that many more electrons.

What is the difference between a compound and a mixture?

The components of a mixture are not chemically bonded together.

When a hydronium ion concentration equals 1 10-10 moles per liter, what is the pH of the solution? Is the solution acidic or basic?

The pH of this solution is 10, which is basic.

In terms of the periodic table, is there an abrupt or gradual change between ionic and covalent bonds?

There is a gradual change: the farther apart, the more ionic.

Why does a glowing splint of wood burn only slowly in air, but rapidly in a burst of flames when placed in pure oxygen?

There is a greater number of collisions between the wood and oxygen molecules.

Would you expect to find more dissolved oxygen in polar or tropical ocean waters? Why?

There would be more dissolved oxygen in the tropical oceans because the heated oxygen molecules in the air would collide with and mix into the water.

One of the products of combustion is water. Why doesn't this water extinguish the combustion?

This water is in the gaseous phase and merely floats away from the fire.

Why is heat often added to chemical reactions performed in the laboratory?

To allow a greater number of reactants to pass over the activation energy To increase the rate at which reactants collide To compensate for the natural tendency of energy to disperse Answer: all of the above

Steel is not listed in the periodic table because it is

a mixture of different elements

If a strong acid has a great tendency to lose hydrogen ions, a strong base has a great tendency to

gain them.

The difference between an exothermic and endothermic reaction is that an exothermic reaction

has energy as a product, and an endothermic reaction has energy as a reactant.

A hydrogen atom does not form more than one covalent bond because it

has only one electron to share.

The atoms of materials that conduct electricity best tend to be held together by

metallic bonds

What type of chemical bond would you expect between two chlorine atoms (Cl, atomic number 17)?

nonpolar covalent

Carbon dioxide makes rainwater acidic by

reacting with the water to form carbonic acid.

A refrigerator delays the spoilage of food by

slowing down the rate of chemical reactions within microorganisms.

The purpose of coefficients in chemical equations is to make

the number of times each element appears as a reactant and as a product the same.

The valence electrons of elements in the same atomic period are similar because elements in the same atomic period have the same number of

unpaired valence electrons. paired valence electrons. valence electrons. answer: none of the above