Module 5

How many electrons are used to draw the electron-dot structure for hydrogen peroxide (a covalent compound with the formula H2O2)?

14

What is the mass of an oxygen atom, O, in atomic mass units?

16 amu

How much energy is released upon the formation of the bonds within 1 mole of hydrazine, N2H4?

1715kJ

What is the mass of a water molecule, H2O, in atomic mass units?

18 amu

Which has the greatest number of atoms?

32 grams of methane, CH

Which set of coefficients balance the following chemical equation? ____ PH3 + ____ O2 ____ P4O10 + ____ H2O

4,8,1,6

How many grams of sodium chloride are needed to make 15 L of a solution that has a concentration of 3.0 g per liter of solution?

45g

How many molecules of aspirin (formula mass aspirin = 180 amu) are there in a 0.250 gram sample?

8.38 x 10^20

Are the chemical reactions that take place in a disposable battery exothermic or endothermic? Is the reaction going on in a rechargeable battery while it is recharging exothermic or endothermic?

An operating disposable battery is driven by exothermic reaction, while a recharging rechargeable battery is driven by endothermic reactions.

Why might softened water not be good for some one who is trying to reduce their dietary sodium ion intake?

Because water softeners work by replacing the calcium and magnesium ions of the water with sodium ions, softened water contains increased levels of sodium ions.

If gallium ions have a 3+ charge and a sulfur ions have a 2- charge, the compound gallium sulfide is

Ga2S3

Many people hear about atmospheric ozone depletion and wonder why we don't simply replace that which has been destroyed. Knowing about CFCs and how catalysts work, explain how this would not be a lasting solution.

Governments would be too slow to respond as they argued about who should shoulder the burden of undertaking such an endeavor. The amount of energy required to create and transport sufficient ozone to the stratosphere would be cost prohibitive. Any ozone we placed into the stratosphere would be destroyed by the same catalytic action that destroys naturally occurring stratospheric ozone.

Why is a ruby gemstone considered to be a solution?

It is a homogeneous mixture of chromium in aluminum oxide.

Which solute graphed in the figure shown above has a solubilty in water that does not markedly increase with increasing temperature?

NaCl

Why do nonpolar substances tend to boil at relatively low temperatures?

Not much heat is required to separate nonpolar molecules from one another.

What would be a major advantage and a major disadvantage of desalinizing water by freezing?

The supply of ocean water is vast, but this technique is limited to northern coastal regions. The supply of ocean water is vast, but ocean water is too salty to make this method cost efficient. The supply of ocean water is vast, but time and energy is better spent hauling icebergs to coastal regions in need of fresh water.

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.

Why is it important to conserve fresh water?

There is little fresh water available to us on our planet. It is expensive to purify nonpotable water. As the human population grows, so does our need for fresh water.

Why is it so easy for a magnesium atom to lose two electrons?

These two electrons are well shielded from the nuclear charge

What do chicken noodle soup and garden soil have in common?

They are both examples of heterogeneous mixtures.

If you had 1 mole of marbles, how many marbles would you have?

a very large number

Atoms or ions can be blended in any proportion within

an alloy

Is the decomposition of food by bacteria in our digestive systems aerobic or anaerobic?

anaerobic because very little air gets to our intestines

A chemical mixture is distinguished from a chemical compound in that

chemical compounds may be found in a chemical mixture.

Many dry cereals are fortified with iron, which is added to the cereal in the form of small iron particles. How might these particles be separated from the cereal?

collect the iron filings with a magnet

What elements tend to form ionic compounds?

elements found on opposite sides of the periodic table metallic elements

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.

Chemical mixture

heterogeneous mixture, no chemical bonds

How might you separate a mixture of sand and salt?

just add water heat the mixture until one of the components melts with tweezers and a magnifying glass Correct: Two of the above answers are reasonable

Carefully examine the following reaction sequence for the catalytic formation of ozone, O3, from molecular oxygen, O2. Which chemical compound is behaving as the catalyst? O2 + 2 NO 2 NO2 2 NO2 2 NO + 2 O 2 O + 2 O2 2 O3

nitrogen monoxide, NO

The neon atom tends NOT to lose any electrons because

of its relatively strong effective nuclear charge.

The outer electrons of metal atoms differ from the outer electrons of nonmetal atoms in that the outer electrons of metals

reflect many frequencies of light. can conduct electricity. are loosely held.

Water molecules are attracted to sodium chloride because

the dipoles of water are attracted to the ionic charges.

Detergents differ from soaps in that

their ionically charged heads are derivatives of sulfur.

What are the formula masses of water, H2O; propane, C3H6; and 2-propanol, C3H8O?

water: 18 amu. propene: 42 amu. 2-propanol: 60 amu