sexta-feira, 9 de julho de 2010


1. Sodium chloride is an ionic compound that is solid. Dissolved in water, dissociates completely.
About this salt, it is INCORRECT to say that
(A) has formula NaCl.
(B) in solid form, the attraction between its ions is very strong and therefore has a high melting point.
(C) in aqueous solution, conducts electric current very well.
(D) the connection between its ions is by covalency.
(E) HCl and  NaOH are the acid and base that give rise to this salt.

2. The element bromine compounds form ionic and molecular. Which alternative form respectively an ionic compound and a molecular compound of bromine.
(A) CaBr2 and HBr
(B) CBr4 and KBr
(C) NaBr and MgBr2
(D) KBr and NH4Br
(E) Br2 and  HBr.

3. Chemical characteristics are important indices that characterize the water quality. The main ones are: the extent of  ionic compounds, the measure of productivity evaluation of nutrients and organic content.
Tick the correct alternative in relation to ionic compounds.
(A) KCl is an oxide so do not dissolve in water.
(B) KCl when dissolved in water does not conduct electrical current, is considered a non-electrolyte.
(C) KCl is not ionic.
(D) KCl when dissolved in water conduct electrical current, is considered a strong electrolyte.
(E) KCl is considered a base, since it undergoes dissociation when dissolved in water.

4. In an ionic substance, the number of electrons transferred and received must be the same. Thus, in a formula of  aluminum oxide, the number of electrons is equal to
(A) 2.
(B) 3.
(C) 4.
(D) 5.
(E) 6.

5. Discovered this year by German  researchers, the new chemical element of atomic number 112 will be christened "Copernicium" in honor of the scientist and astronomer Copernicus (1473-1543). According to scientists, the new element is about 277 times heavier than hydrogen, making it the heaviest element of the periodic table, occupying the position relative to the period of the Group 12 7. The Periodic Table, one of the most notable achievements in chemistry, was developed exclusively from physical and chemical properties of the elements and therefore the knowledge of the position occupied by a chemical element allows you to make some predictions about their properties. Considering the location of atoms of chemical elements X, Y and Z in the periodic table:

X = 3 period of Group 1
Y = 3 period of the Group 16
Z = 2 period of the Group 18

is correct to say that
(A) The states allotrope of the element Y are diamond, graphite and fullerene.
(B) the element X and conducts the electrical current in solid state and form an ionic compound when combined with the element Y.
(C) The element Z reacts violently with water, generating hydrogen gas and an Arrhenius base.
(D) The combination of the elements X and Y leads to the formation of a molecular compound.
(E) The element Z has the highest electron affinity, and thus tends to gain electrons more easily than the elements X and Y.

06. The compound HF, which is a colorless gas, is characterized by eroding the glass when it is in aqueous solution. For the HF is INCORRECT to say that
(A) in water undergoes ionization.
(B) in aqueous solution, can be used to make recordings in glasses and crystals.
(C) form hydrogen bonds.
(D) its aqueous solution should be stored in plastic container.
(E) the connection that occurs between hydrogen and fluorine is predominantly ionic.

07. The ability of an atom has to attract electrons from another atom, when the two form a chemical bond is called electronegativity. This is one of the chemical properties considered in the study of polarity of the connections.
Check the box that shows, correctly, the compound  H2O, H2S and H2Se in order of increasing polarity.
(A) H2Se < H2O < H2S
(B) H2S < H2Se < H2O
(C) H2S < H2O < H2Se
(D) H2O < H2Se < H2S
(E) H2Se < H2S < H2O

08. Nitric oxide, NO, is usually conveyed by the media as an undesirable environmental pollutant. It is known, however, that this substance is also essential in the digestive activities in the regulation of blood pressure and bacterial defense, occurring naturally in various cell types of the human body.
Regarding аs chemical bonds present in the molecule of nitric oxide, is correct to say that
(A) are predominantly ionic, resulting in a nonpolar chemical species.
(B) are nonpolar covalent, and the NO molecule is polar.
(C) а satisfy the octet rule, and the oxidation number of nitrogen is +2.
(D) are polar covalent, and the NO molecule has zero dipole moment.
(E) are nonpolar covalent, and the NO molecule has a strong ionic character.

09. On the connection between atoms of the chemical element chlorine, which has atomic number equal to 17, they form a
(A) triatomic molecule.
(B) simple ionic substance.
(C) nonpolar molecule.
(D) polar molecule.
(E) composite gaseous substance.

10. To study the relationship between the type of chemical bonding and physical properties of substances X, Y, а solid at room temperature, experiments were performed to conclude that
- The substance X conducts electrical current in liquid but not solid.
- The substance does not conduct electrical current Y in any state.
Considering that information is correct to say that
(A) a substance X and substance Y is the molecular ion.
(B) a substance X and substance Y is ionic metal.
(C) a substance X is ionic and Y is molecular substance.
(D) substances X and Y are molecular.
(E) substances X and Y are ionic.

1 [D] 2 [A] 3 [D] 4 [E] 5 [B]  6 [E]  7 [E]  8 [D]  9 [C]  10 [C]
Compiled by: Prof.Paulo Silva