CHEM 131 Exam 2

Cyanide

CN-

A Lewis structure with placeholder central atom is shown below. If the charge of the molecule is -1, choose the possible identity or identities of the central atom.

Cl, Br, or I

Hypochlorite

ClO-

Chlorate

ClO3-

Perchlorate

ClO4-

Chromate

CrO4 2-

Define molecule:

Describes compounds in which the atoms are held together by shared electrons.

How do you find mass percent of an element in a compound?

Divide the mass of element (multiplied by its subscript) by the mass of the compound and then multiplying by 100.

The trend towards smaller atomic radii as one moves to the right in a period is _____.

Due to the effective nuclear charge increasing.

Which of the following is true concerning successive ionizations of an atom and its ions?

Each successive ionization requires increasing amounts of energy.

Which one of the following is the most electronegative atom? a. C b. N c. O d. F

F

What is the most electronegative element?

Fluorine

Write the chemical formula for the hydrogen phosphate ion

HPO4 2-

What are two periodic trends that parallel electronegativity?

Ionization energy and electron affinity.

Which periodic trend quantifies the amount of energy required to remove an electron from a neutral, gaseous atom?

Ionization energy; the amount of energy required to remove an electron from a neutral, gaseous atom.

What is the correct IUPAC name for Fe(NO₃)₃ · 6H₂O?

Iron (III) nitrate hexahydrate

Ammonium

NH4+

Phosphate

PO4 3-

Sulfate

SO4 2-

Define excess reactant

The excess reactant is defined as any of the other reactants still present after the consumption of the limiting reactant.

Show how to solve for percent yield

% yield of chemical reaction= (actual yield/ theoretical yield) *100

Naming binary compounds:

- Metal; non-metal- IDE - Number of ions doesn't need to be specified in the name.

Naming binary compounds that contain two non-metals:

- Prefix- first element; prefix- second element- IDE. Ex: N2O4= di nitrogen tetra oxide - Mono is NOT used for the first atom. Ex: CO2= carbon di oxide

Linear Shaped

1 or 2 electron domains; 180 degrees; no lone pairs.

A particular protein sample is found to have 1 atom of iron in its chemical formula. If the mass percent of Fe in the compound is 0.330% Fe, what is the molar mass of the protein?

16900 g/mol 55.80 gFe/1mol Fe x 1mol Fe/1mol cmpd x 100 g cmpd/0.330 gFe= 16900

Tetrahedral Bent Shaped

4 electron domains; 109.5 degrees; two lone pairs.

If 5.9 × 10²⁵ molecules of CO₂ are produced in a combustion reaction, what is the mass in kg of CO₂ that is produced?

4.3 kg 5.9*10^25 molecules of CO2 x (1mol/6.022*10^23 molecules of CO2) x (44.01 g/1mol) x 1kg/1000g)= 4.3 kg

Trigonal Bipyramidal

5 electron domains; 90, 120, and 180 degrees; no lone pairs.

What is the correct IUPAC name for Al(HSO₄)₃?

Aluminum hydrogen sulfate

What is the correct IUPAC name for AlPO₄?

Aluminum phosphate

Define covalent compounds:

They are typically made of two or more non-metals, and characterized by the atoms sharing their electrons in covalent bonds.

Linear Hybridization:

sp

Trigonal Planar Hybridization:

sp^2

Tetrahedral Hybridization:

sp^3

Trigonal Bipyramidal Hybridization:

sp^3d

Octahedral Hybridization:

sp^3d^2

Which atomic orbitals from carbon hybridize to form the bonds in CH₄?

2s, 2p_x, 2p_y, 2p_z When you draw the orbital energy diagram for C to find where its valence electrons are. They are found in 2s,2pₓ,2py,2pz.

Trigonal Planar Shaped

3 electron domains; 120 degrees; no lone pairs.

Trigonal Planar Bent Shaped

3 electron domains; 120 degrees; one lone pair.

Trigonal Planar Linear Shaped

3 electron domains; 120 degrees; two lone pairs.

Tetrahedral Shaped

4 electron domains; 109.5 degrees; no lone pairs.

Trigonal Pyramidal Shaped

4 electron domains; 109.5 degrees; one lone pair.

Seesaw Shaped

5 electron domains; 90, 120, and 180 degrees; one lone pair.

Trigonal Bipyramidal Linear Shaped

5 electron domains; 90, 120, and 180 degrees; three lone pairs.

Trigonal Bipyramidal T-shaped

5 electron domains; 90, 120, and 180 degrees; two lone pairs.

Octahedral Shaped

6 electron domains; 90 and 180 degrees; no lone pairs.

Square Pyramidal Shaped

6 electron domains; 90 and 180 degrees; one lone pair.

Octahedral T-shaped

6 electron domains; 90 and 180 degrees; three lone pairs.

Square Planar Shaped

6 electron domains; 90 and 180 degrees; two lone pairs.

How many valence electrons are in a neutral atom of chlorine?

7

What is the mass percentage of C in CH₃CH₃?

79.88% ((12.01g*2)/30.07g)*100= 79.88%

Carbonate

CO3 2-

Write the chemical formula for the carbonate ion

CO3 2-

Predict the chemical formula for the ionic compound formed by Ca²⁺ and ClO₃⁻

Ca(CLO)2

The energy released in the reaction F(g) + e⁻ → F⁻(g) is known as the

Electron affinity; the change in energy when an electron is added to a neutral gaseous atom to form an ion.

Rank the following atoms in order of decreasing first ionization energies (i.e., highest to lowest): Li, Be, Ba, F.

F>Be>Li>Ba

Define theoretical yield

It is always a calculated value based on the limiting reactant.​

Define empirical formula

It reflects the smallest whole number ratio of elements in the compound.

Naming ionic compounds involving a transition metal:

Metal (charge); non-metal- IDE Ex: Fe3+= iron (III)

Naming ionic compounds involving polyatomic ions:

Metal (charge); polyatomic ion

Which of the following pairs of ions represent isoelectronic species?

Mg2+ and O2-

Write the chemical formula for manganese(II) bromite

Mn(BrO2)2

Consider the fourth period elements Ca, Mn, Co, Se, and Kr. Which of these atoms are paramagnetic?

Mn, Co, Se

Define compound:

More general term used to describe a group of atoms combined in a specific ratio.

Define the octet rule:

Most main group elements would gain, lose, or share electrons in order to achieve a full valence shell of 8 electrons.

A Lewis structure with placeholder elements is shown below. If the formal charge of the central atom is +1, choose the possible identity or identities of the central atom.

N, P, or As

Nitrate

NO3-

Hydroxide

OH-

Write the chemical formula for tin(II) chloride dihydrate

SnCl2*2H2O

Which of the following atoms is diamagnetic?

Sr (does not have any unpaired electrons)

What is one way you could predict molecular polarity?

The larger the electronegativity difference between 2 atoms, the more polar a bond will be.

Atomic radii decrease from left to right in a period (Na → Ar) on the periodic table. Choose the best explanation for this observed trend.

The nuclear charge increases in that direction.

Define limiting reactant

The reactant that limits the amount of product that can be formed. The limiting reactant is always completely consumed during the course of the reaction.

What happens to non-metals when they become ions?

They have a negative charge.

What happens to metals when they become ions?

They have a positive charge.

Define ionic compounds:

They usually are composed of a metal and a non-metal, where one or more electrons have been transferred away from the metal, making it a positively charged cation, giving the electron to the nonmetal making it a negatively charged anion. (Ex: Na loses an electron= Na+; Cl gains and electron= Cl-; forming the compound NaCl.)

What is the correct IUPAC name for Ti(ClO₄)₄?

Titanium (IV) perchlorate