Chem exam 2

Atoms of nonmetallic elements form covalent bonds, but they can also form ionic bonds. How is this possible?
An ionic bond results when a nonmetallic elements gains an electron from a metallic element.
Phosphine is a covalent compound of phosphorus, P, and hydrogen, H. What is its chemical formula?
Water, H2O, and methane, CH4, have about the same mass and differ by only one type of atom. Why is the boiling point of water so much higher than that of methane?
The oxygen of a water molecule has two lone pairs of electrons, the water molecule is less symmetrical than is the methane molecule, the electronegativity difference between oxygen and hydrogen is greater than the electronegativity difference between carbon and hydrogen.
Why does the solubilities in water go down as the boiling points of these alcohols go up?
Larger molecules are more attracted to one another by induced dipole-induced dipole as well as by dipole-dipole and dipole-induced dipole attractions.
Based on atomic size, which would you expect to be more soluble in water: helium, He, or nitrogen, N2?
Nitrogen atoms are bigger and so nitrogen molecules should be more soluble in water due to greater dipole-induced dipole attractions.
How can you tell whether a sugar solution is saturated or not?
Cool the solution to see if there is a precipitate.
Hydrogen chloride, HCl, is a gas at room temperature. Would you expect this material to be very soluble or not very soluble in water?
HCl very soluble in water by virtue of the dipole/dipole attractions occurring between the HCl and H2O molecules.
Two chemical structures are shown, one of a typical gasoline molecule and the other of a typical motor oil molecule. Which is which? Base your reasoning not on memorization but rather upon what you know about molecular interactions and the various physical properties of gasoline and motor oil.
Structure A represents motor oil, illustrating a molecule with greater induced dipole-induced dipole molecular interactions thus, the molecules are strongly attracted to one another.
Account for the observation that ethyl alcohol, C2H5OH, dissolves readily in water but dimethyl ether, CH3OCH3, which has the same number and kinds of atoms, does not.
Because dimethyl ether lacks an -OH group, it is significantly less polar than is ethyl alcohol and is not readily soluble in water.
An inventor claims to have developed a new perfume that lasts a long time because it doesn't evaporate. Comment on this claim.
In order to smell something, the molecules must evaporate and reach your nose. If the new perfume doesn't evaporate, it will not have an odor.
Which has more atoms: 17.031 g of ammonia, NH3, or 72.922 g of hydrogen chloride, HCl?
72.922 g of HCl has more atoms than 17.031 g of NH3.
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.
Suggest why people once washed their hands with ashes.
The ashes act as a base and reacts with skin oils to produce solutions of soap.
Sodium hydroxide, NaOH, is a strong base, which means that it readily accepts hydrogen ions. What products are formed when sodium hydroxide accepts a hydrogen ion from a water molecule?
water and sodium hydroxide
What does the value of Kw say about the extent to which water molecule react with themselves?
Since the value of Kw is so small, the extent to which water ionizes is quite small.
When the hydronium ion concentration equals 1 mole per liter, what is the pH of the solution? Is the solution acidic or basic?
pH = 0, this is an acidic solution.
Why might a small piece of chalk be useful for alleviating acid indigestion?
Calcium carbonate is a base that reacts to neutralize any excess acids.
Hydrogen chloride is added to a buffer solution of ammonia, NH3, and ammonium chloride, NH4+Cl -. What is the effect on the concentration of ammonia? What is the effect on the concentration of ammonium chloride?
HCl reacts with only the ammonia, so the concentration of the ammonium chloride increases and the concentration of ammonia decreases.
When a hydronium ion concentration equals 1 10-4 moles per liter, what is the pH of the solution? Is the solution acidic or basic?
The pH is of this solution is 4 and it is acidic.
How many structural isomers are there for hydrocarbons having the molecular formula C4H10
Why might a high-formula-mass alcohol be insoluble in water?
The bulk of a high formula mass alcohol likely consists of nonpolar hydrocarbons.
If you saw the label phenylephrine·HCl on a decongestant, would you worry that consuming it would expose you to the strong acid hydrochloric acid, HCl?
No, because this is a salt made using hydrogen chloride, but it is in no way hydrogen chloride.
Which would you expect to be more viscous, a polymer made of long molecular strands or one made of short molecular stands? Why?
Long molecular strands because they tend to tangle among themselves.