CHEM 1110- Exam 2 chp. 4-6
Determine the number of atoms of each type on each side of the following equations and state whether the equation is balanced or not 1) Na + Cl₂ → NaCl 2) 3Ag₂S + 2Al → 6Ag + Al₂S₃ 3) CH₄ + 4Cl₂ → CCl₄ + 4 HCl
1) reactants: one Na atom, two Cl atoms, products: one Na atom, one Cl atom. *Not balanced* 2) reactants: six (3 x 2) Ag atoms, three (3 x 1) S atoms, and two Al atoms, products: six Ag atoms, two Al atoms, and three S atoms. *Balanced* 3) reactants: one C atom, four H atoms and eight (4 x 2) Cl atoms, products: one C atom, eight Cl atoms (four from CCl4 and four from the 4 HCl molecules), and four H atoms. *Balanced*
1) Na+ and NO3- 2) Mg2+ and SO42- 3) K+ and MnO4- 4) NH4+ and CN-
1) sodium nitrate, 2) magnesium sulfate, 3) potassium permanganate, 4) ammonium cyanide
In a chemical equation, the coefficient before the compound formula times the subscript give the total number of atoms. Calculate how many atoms are represented in each of these examples: 1) 2H2 2) 2H2O 3) 2(NH4)2S
1) there are 2x2 atoms of hydrogen (a total of 4) 2) there are 2x2 atoms of hydrogen (a total of 4) and 2x1 atoms of oxygen ( a total of 2) 3) Be careful with this one! Realize that there are 2 units of (NH4)2S and that each unit has 2 NH4+ groups in it and even NH4+ has one N in it, so there are 2x2x1 atoms of nitrogen ( a total of 4), there are 2x2x4 atoms of hydrogen ( a total of 16), and 2x1 atoms of sulfur (a total of 2)
Naming Binary Covalent Compounds
1. Give the full name of the less electronegative element first. 2. Next, give the stem of the more electronegative element and follow it with the suffix -ide (refer to Table 4.2). 3. Finally, by using the Greek prefixes, mono(1), di(2), tri(3) tetra(4), pent(5) indicate the number of each type of atom. The prefix mono is not used when it appears at the beginning of a name
2Ca + O₂ --> 2CaO How many grams of CaO can be produced from 1.80 moles of Ca with an unlimited supply of O₂?
101 g
Molecular
2K(s) + H₂SO₄(aq) --> K₂SO₄(aq) + H₂(g) The reaction above is an example of a ________ equation.
How many different compounds are in a double-replacement reaction?
4 Metathesis reactions (more commonly known as double-replacement reactions) occur when two compounds react and swap partners, thus forming two new compounds. In general terms the formula looks like this: AX + BY → BX + AY
What is the maximum number of grams of Cr that can be produced from 100. g of Cr2O3 and 100. g of Al using the reaction below: Cr₂O₃ + 2Al ---> 2Cr + Al₂O₃
68.0 g
In covalent bonds, each atom strives to have ________ electrons in its valence shell (except for H, Li, Be and B which only need 2 electrons in their valence shell)
8
For a combination reaction, it was calculated that 8.0g of A would exactly react with 3.5g of B. These amounts were reacted, and 10.5g of product was isolated. What is the percentage yield of the reaction?
91%
right (product)
A + B --> C If the reaction above were exothermic, "heat" would be added to the _____ side of the equation
limiting reactant
A compound that determines the amount of product made during a reaction
Using the law of conservation of matter, predict how many grams of product will be produced if 54.0 grams of aluminum completely reacts with 48.0 g of oxygen.
Because matter is not created or destroyed, the total mass of the products must equal the total mass of the reactants: 54.0g + 48.0 g = 102.0g Therefore, 102.0g of products would be formed.
6.0 Moles
CH₄+ 4Cl₂ --> CCl₄ + 4HCl Using the above reaction, how many moles of HCl can be produced from 1.5 moles of CH4?
a.Ca^2+ b.F- c.SO₄^ 2- d.H + e.more than one choice is correct F. NO CORRECT RESPONSE
CaF2(s) + H2SO4(aq) --> CaSO4(s) + 2HF(g) In the reaction above, the dissolved substances designated by (aq) are the only ones that dissociate completely into ions. Write the reaction above in total ionic form. What is(are) the spectator ion(s)?
polar molecule
Contains partial positive charges and partial negative charges distributed non-symmetrically.
single replacement
Cr2O3 + 2Al --> 2Cr + Al2O3 The above is an example of what kind of reaction?
Electronegativity trends
Due to the unequal electron sharing in polar covalent bonds, the more electronegative atom takes on a partial negative charge (d-) while the less electronegative atom takes on a partial positive charge (d+)
Covalent Bonding
Elements with tendancy to gain or lose electrons often react and achieve nobel gas electronic configurations by sharing electrons. Shared pairs of electrons exert an attractive force on both atoms that share them.
Na+, I-
H+ + I- + Na+ + OH- --> Na+ + I- + H₂O What is(are) the spectator ion(s) in the above reaction?
Write the following equation in the total ionic format: HBr(aq) + KOH (aq) → KBr(aq) + H₂O(l) ₂₃₄
H+(aq) + Br-(aq) + K+(aq) + OH-(aq) → K+(aq) + Br-(aq) + H₂O(l) When writing a total ionic equation, all soluble ionic substances are written as the ions they form in solution followed by the (aq) symbol. The symbols l, g and s are written after compounds that do not dissociate into ions, but remain in the form of undissolved liquids (l), gases (g) or solid (s)
How would the covalent bonding between H and F be correctly represented?
H:F:
double replacement reaction
HBr + KOH --> KBr + H2O The reaction above is an example of a
The interparticle forces between water molecules are known as ________.
Hydrogen bonds A strong dipolar force can exist between molecules in which hydrogen atoms are covalently bonded to very electronegative elements (O,N or F). This is referred to as hydrogen bonding (see Figure 4.10). The relatively high boiling point of water and the crystalline structure of ice can be attributed to the hydrogen bonding that occurs between water molecules. Hydrogen bonding is not a real "bond", it is an attraction between hydrogen atom on one molecule and a highly electronegative atom on another molecule (usually an O, N or F atom) Because it is an attraction and not a real bond it is represented as a dashed (---) line. For example, let's look at hydrogen bonding between ammonia (NH3) molecules. The electronegative N atom draws electrons to it, making it partially negative in charge and the H's partially positive in charge. Therefore, the H on one NH3 molecule is attracted to the N on another molecule (the partial + charge attracts to the partial - charge), and this attraction is represented as a dashed line. It is important for you to understand hydrogen bonding because it determines the physical properties of many compounds in future chapters.
Zn^2+, 2Br -
If ZnBr2 were to dissociate in water, what ions would be produced?
________ bonds form when oppositely-charged simple ions are attracted to one another.
Ionic When simple ions have opposite charges, they are attracted to one another, and the attractive force that holds them together is called an ionic bond.
Ionic Bonding
Ionic compounds are formed when reacting atoms gain or lose electrons to achieve a nobel gas confiuration of eight electrons in the valence shell. This octet rule predicts that atoms will be changed into charged particles called simple ions. Ions od opposite charge are attracted to each other; the attractive force is called an ionic bond
Ionic Compound Names
Ionic compounds that contain a metal ion (or ammonium ion) plus a polyatomic ion are named by first namind the metal (or ammonium ion) followed by the name of the polyatomic ion.
Atoms that lose or gain electrons are known as simple ________. If an atom gains electrons it will become ________ charged. If an atom loses electrons, it becomes ________ charged.
Ions, Negatively, Positively In some cases, electrons are transferred from one atom to another in order to have 8 electrons in the valence shell. These atoms then become positively or negatively charged and are called simple ions. Atoms that lose electrons become positively charged (the loss of negative charged electrons means there are more positive protons than negative electrons). Atoms that gain electrons become negatively charged (gain negative charges).
Polyatomic Lewis Structures
Lewis structures can be drawn for polyatomic ions. However, there are a couple of differences from determining regular electron dot formulas. First, determine the number of valence electrons in each atom and add them up. Then take a look at the charge on the polyatomic ion. Remember that electrons have a charge of -1; therefore, if the ion charge is -3, that constitutes 3 electrons which must be added to the original valence electrons in the Lewis structure. Likewise, if the ion charge is positive, that many electrons must be subtracted from the structure. Finally, to finish off the Lewis structure, brackets are drawn around it and the charge is written on the upper right side (outside the brackets)
What type of interparticle forces is found in a sample of sodium (Na)?
Metallic In general, metals have low electronegativities and are easily ionized. This leads to metallic bonding that holds metal atoms together. In this type of bond, the metal atoms lose their valence-shell electrons, leaving positively charged "kernels" to occupy lattice sites surrounded by a "sea" of mobile electrons. Electricity is easily conducted through metals' bonds because electrons can move freely about.
Interparticle forces
Metallic bonds, dipolar attractions, hydrogen bonds, and dispersion forces.
Hydrogen bonding can exist between identical molecules in which of the following pure substances?
NH₃
Naming Binary Covalent compounds
Name of the less electronegative element, followed by the stem plus -ide of the more electronegative element. Greek prefixes ARE USED
According to the ________ rule, all atoms will lose or gain electrons in order to achieve a valence shell with eight electrons.
Octet The octet rule states that all atoms tend to strive for a noble gas configuration (that is 8 electrons) in their valence shell by interacting with other atoms.
Determine the number of each type of atom on both sides of the following equation. Is the equation balanced? Has the law of conservation of matter been followed? CuO + H₂ → Cu + H₂O
On the reactant side of the equation, there is one Cu atom, one O atom, and two H atoms (remember the subscript tells how many atoms are in a molecule). On the product side there is one Cu atom, two H atoms, and one O atom. No atoms have been created or destroyed; thus, the equation is balanced and the law of the conservation of matter is obeyed. By counting the number of each type of atom on both sides of the equation, we can gain a better understanding of what a balanced equation is and what the law of conservation of matter really means.
Ionic Compounds
Oppositely charged ions roup together to from compounds in ratios determined by the positive and negative charge of the ions
decomposition
PbCO3 --> PbO + CO2 The above is an example of what kind of reaction?
Nobel Gas Configuration
The lack of reactivity for nobel gases lef to the proposal that the electronic configurations of the nobel gases represented stable configurations. These configurations, usually consisting of 8 electrons in the valence shell can be represented in several useful ways.
Manganese (Mn) can have a +4 or +6 charge. What compound would result if Mn4+ ironically bonded with SO42-?
The largest charge is +4, and two -2 charges are needed to cancel out the positive charges: +4 + 2(-2) = +4 - 4 = 0 So the formula is: Mn(SO4)2
Polarity of Covalent Molecules
The tendancy of a covalently bonded atom to attract shared electrons is called the electronegativity of the atom.
electronegativity
The tendency of an atom to attract shared electrons of a covalent bond.
dispersion force
The weakest of interparticle attractive forces caused by momentary nonsymmetric electron distributions in molecules.
Name Binary Ionic Compounds
To name binary ionic compounds give the full name of the metal element first, then the stem of the nonmetallic element followed by -ide. Remember the equation: binary ionic compound name = metal + nonmetal stem + ide
Ca → Ca²+ + 2e-
Use the periodic table to predict how Ca would gain or lose electrons during ion formation.
In electron dot formulas, the dots around an element's symbol represent ________ electrons.
Valence: Lewis structures or electron dot formulas are ways of representing the elements so more information is provided. In electron dot formulas, the element's symbol represents the nucleus and all of its electrons except those in the valence shell. Valence shell electrons are represented as dots around the symbol. Remember, valence electrons are the ones found in the outermost (highest energy) shell of an atom.
ΔEN
We have discussed ionic, nonpolar covalent, and polar covalent bonds. The type of bond depends on whether electrons are exchanged or shared. Differences between the electronegativities of the bonded atoms can be used to classify the bond type. (ΔEN) 0.0, the bond is classified as nonpolar covalent (the electrons are shared equally) ΔEN is 2.1 or greater, the bond is classified as ionic (the electrons are transferred). ΔEN is between 0.0 and 2.1, the bond is classified as polar covalent (the electrons are unequally shared, and the bond is polarized).
2,2,1
What coefficients are needed to balance the following reaction? _______ H2O2 --> _____ H2O + _____ O2
diphosphorus pentoxide
What is the name for the covalently bonded P₂O₅ molecule?
aluminum oxide
What is the name for the ionic compound Al₂O₃?
BaI₂
What would the formula be if barium (Ba) and iodine (I) were to form an ionic compound?
Drawing Lewis Structures
When drawing Lewis structures or electron dot formulas for elements, the key is to determine the number of valence electrons. One way to do this would be to write an electron configuration for the element and find the electrons in the outermost shell. However, a quicker, easier way is to simply look at the group number of the element in question. It must be the number preceding the "A" above each group. This number is the same as the number of valence electrons for that element
Writing formulas for compounds containing polyatomic ions
When writing formulas for compounds containing polyatomic ions, the rules are essentially the same as those used earlier for binary ionic compounds. In the formulas, the number of positive and negative charges must be equal to each other, and parentheses are used around the polyatomic ions if more than one is used
OF₂
Which compound exhibits that greatest amount of covalent bonding?
lose one electron
Which of the following would cause a potassium atom (K) to achieve a noble gas configuration?
How would the bonding in the CN- polyatomic ion be correctly represented?
[:C:::N:]-
In general, metals will become ________ charged and nonmetals ________ charged during ionic bond formation.
positively, negatively In general, to satisfy the octet rule, metals lose electrons and nonmetals gain electrons during ionic bond formation.
The substances that undergo chemical change in a chemical reaction are known as the ________.
reactants In chemical equations, the reactants are the substances that undergo chemical change. They are written on the left side of the equation
Label the products and reactants in the following equation: H₂S + I → 2HI + S
reactants: H₂S and I₂, products: HI and S
A(n) ________ ________ or _______ reaction occurs when an element reacting with a compound displaces one of the elements in the compound
single replacement or substitution Single-replacement, or substitution, reactions occur when an element reacts with a compound and switches places with one of the elements in the compound. The general formula for this type of reaction is: A + BX → B + AX.
________ ions appear on both the left and right sides of the balanced total ionic equation, indicating that they do not experience any change in the reaction.
spectator When a balanced reaction is written as a total ionic equation, some of the ions appear in equal numbers as both reactants and products. These ions are known as spectator ions because they do not undergo any changes in the reaction.
Identify all spectator ions and write the following total ionic equation as a net ionic equation: 2Na+(aq) + 2I-(aq) + Pb2+(aq) + 2NO₃- (aq) → PbI2(s) + 2Na+(aq) + 2NO₃-(aq)
spectator ions: 2Na+, 2NO₃- net ionic = 2I-(aq) + Pb^2+(aq) → PbI₂(s) After the balanced total ionic equation has been written, identifying spectator ions and writing the net ionic equation are the next steps. Net ionic equations are nothing more than total ionic equations minus all spectator ion
dipolar force
The attraction between the positive end of a polar molecule and the negative end of another polar molecule.
covalent bond
The attractive force between two atoms attracted to a shared pair of electrons.
When an equation is ________ it has equal numbers of the same atoms in the reactants and the products.
balanced To comply with the law of conservation of matter, written equations need to be balanced, that is each kind of atom will have equal numbers on the reactants and products side of the equation.
A(n) ______ reaction begins with two reactants but yields only one product.
combination, addition or synthesis Combination reactions, are like decomposition reactions in reverse. In combination reactions, two or more substances react to form a single product. Combination reactions are also known as addition or synthesis reactions. The general formula for this type of reaction is: A + B → C
The law of ________ of matter states that atoms are neither created nor destroyed in chemical reactions, only rearranged.
conservation There is a fundamental law of nature called the law of conservation of matter that states that atoms are neither created nor destroyed in chemical reactions, but rather just rearranged to form new substances.
Atoms share valence electrons in ________ bonding. If sodium (Na) was to bond with fluorine (F), a(n) _____ bond would form. If sulfur (S) was to bond with oxygen (O), a(n) _____ bond would form.
covalent, ionic (it is a metal bonding with a nonmetal), covalent (it is between two nonmetals
Weak interparticle forces between oppositely charged portions of polar molecules are referred to as ________ forces.
dipolar Because of nonsymmetrical charge distributions in polar molecules, attractive dipolar forces exist between the positive portion of one molecule and the negative portion of another molecule.
Momentary dipoles create ________ forces that weakly attract all particles to each other.
dispersion Dispersion forces are weak attractive forces that act between the particles of all matter. These forces result from short-lived attractions of momentary dipoles.
Going from weakest to strongest, what is the correct arrangement of interparticle forces?
dispersion forces, dipolar forces, hydrogen bonds, covalent bonds
The degree to which an atom attracts the shared electrons in a covalent bond is known as that atom's ________.
electronegativity Atoms of different elements have varying tendencies or strengths for attracting shared electrons in a covalent bond. This tendency or strength is known as electronegativity. The larger the electronegativity number, the more an atom draws the shared electrons to itself.
As the strength of the interparticle forces that hold a pure substance together increases, the melting and boiling points of the substance ________ (increases/decreases).
increases
PO₄3- is the phosphate polyatomic ion. What is the name for the ionic compound Fe₃(PO₄)₂? Note: Fe occurs in both Fe2+ or Fe3+ forms.
iron (II) phosphate
The term ________ refers to atoms or ions that have exactly the same electronic configurations.
isoelectronic When atoms or ions have identical electronic configurations, they are said to be isoelectronic.
Ionic compounds are formed as metals and nonmetals react with one another; ________ lose electrons and ________ gain electrons.
metals, nonmetals Metal atoms lose electrons which are then gained by nonmetal atoms during a chemical reaction. Substances that are formed from this type of reaction are called ionic compounds.
HCl + NaOH → NaCl + H₂O is an example of a(n) ________ equation
molecular
In ________ covalent bonding, shared electron pairs are equally attracted to the two identical atoms.
nonpolar In covalent bonding, when an electron pair is shared by two atoms that are identical, the bond is described as nonpolar covalent. In this type of bonding, the electrons are equally attracted to each of the atoms and the electrons are shared equally.
How many reactants are in a decomposition reaction? How many products?
one reactant, two products In decomposition reactions a single substance is broken down to form two simpler substances. A general formula for this type of reaction would be A → B + C.
When electron pairs are unequally shared between atoms of different types, the resulting bond is known as a ________ covalent bond.
polar Differences in electronegativity mean that electron pairs shared between different types of atoms are not shared equally. The shared electrons move nearer to the atom with higher electronegativity. This shift is known as bond polarization and results in a polar covalent bond.
Groups of atoms that carry a net electrical charge, yet are covalently bonded, are called ________ ions.
polyatomic Polyatomic ions are groups of atoms that are covalently bonded together and yet carry a positive or negative charge. Examples include ammonium NH4+ and sulfate SO42
The correct formula for the ionic compound containing Al3+ and SO₄2- would be
Al₂(SO₄)₃
hydrogen bonding
An attractive force between molecules that have hydrogen atoms bonded to very electronegative atoms.
spectator ion
An entity that does not undergo a change as a reaction proceeds.
octet rule
Atoms gain or lose electrons to achieve an outer electron arrangement identical to a noble gas.
You will also need to calculate the charge on a metal ion in an ionic compound to give the correct Roman numeral in its name. To do this, just find out how many total negative charges there are and then divide that number by how many metal ions there are and change the sign to a +.
PbO2 Oxygen (O) is in Group VI A (6A), and therefore will have a 2- charge. There are 2 oxygen ions (O2) each with a 2- charge. This makes a total of 4- charges. There is only one Pb ion, so 4-/1 = 4-, and we change the sign to become 4+. The charge on the Pb ion is 4+. Because the Roman numeral in the name is the same as the charge on the metal ion, the name of the compound would be lead (IV) oxide a) SnF4 b) Cu2O c) HgS d) Fe2O3 e) MnS2 f) HgI2 a) There is a total -4 charge (4 x -1) and only one Sn ion, so it must have a +4 charge: tin (IV) fluoride. b) One O2- for a total -2 charge. But there are 2 copper ions, so each must be a +1: copper (I) oxide. c) One S2- for a total -2 charge and only one mercury ion: mercury (II) sulfide. d) Three O2- for a total 6- charge. There are 2 iron atoms, so 6-/2 = 3-, the charge on each ion would be 3+: iron (III) oxide. e) Two S2- for a total -4 charge and only one manganese ion: manganese (IV) sulfide. f) Two I- for a total -2 charge and only one mercury ion: mercury (II) iodide.
Polyatomic Ions
Polyatomic ions are groups of two or more covalently bonded atoms that carry a net electrical charge.
endothermic reaction
Reaction that absorbs heat (energy) when it takes place.
exothermic reaction
Reaction that gives off heat as the process occurs.
molecular equation
Reaction that shows all compounds represented by their formulas.
total ionic equation
Reaction that shows all ions involved in the process.
net ionic equation
Reaction that shows ions that actually undergo a change.
Tell whether elements will gain or lose electrons when an ionic bond is formed:
Remember, groups with Roman numerals (or Arabic numerals) followed by "A" are referred to as representative elements. The number of electrons lost by a representative METAL atom is the same as the Roman numeral group number. The number of electrons gained by a representative NONMETAL atom is equal to eight minus the Roman numeral group number (see periodic table inside front cover). Elements in group IA (1A) will lose 1 electron and become 1+ in charge. Elements in group IIA (2A) will lose 2 electrons and become 2+ in charge. Aluminum (Al) will lose 3 electrons and become 3+ in charge. Elements in group VIA (6A) will gain 2 electrons and become 2- in charge. Elements in group VIIA (7A) will gain 1 electron and become 1- in charge. Nitrogen (N) and phosphorus (P) will gain 3 electrons and become 3- in charge.
Name Ionic Compounds containing transition and inner-transition elements
Some metal atoms, especially those of transition and inner-transition elements, are capable of forming more than one type of charged ion. For instance, iron can form Fe2+ and Fe3+. Therefore, when naming ionic compounds that contain these elements, it must be indicated which ion is present in the compound. In order to do this, the ionic charge of the metal ion is indicated as a Roman numeral in parentheses following the name of the metal. So, FeCl2 would be named iron (II) chloride while FeCl3 would be iron (III) chloride
In the formation of ionic compounds, metal and nonmetal ions combine in small whole number ratios so that all the electrons lost by the metal atoms are given homes with the nonmetal atoms. In that way, no electrons are created or destroyed by the process. The reaction of potassium with nitrogen can be used to illustrate the three-step method of arriving at correct formulas for ionic compounds.
Step 1: Write the ionization reactions K→K++1e- (K is in Group IA and will lose 1 e-) N + 3e-→N3- (N is in Group VA and will gain 3e-) Step 2: By doing some simple math, it can be seen that three potassiums are required to supply the three electrons that nitrogen needs to complete its octet: 3K→3K++3e- N + 3e-→N3- Step 3: Write the number of atoms required to provide equal numbers of positive and negative charges as subscripts. The subscript 1 is understood and never written. When writing chemical formulas, the metal is always written first followed by the nonmetal. The correct formula is K3N
4
The Lewis structure for element 32 has ______ electrons (dots) surrounding the symbol Ge.
This balances the equation a) ________ HgO → ________ Hg + ________ O₂ b) ________ H₂ + ________ Cl₂ → ________ HCl c) ________ NaI + ________ Cl₂ → ________ NaCl + ________ I₂ d) ______H₂O₂ → ______ H₂O + ______ O₂ e) ______ N₂ + ______ H₂ → ______ NH₃ f) ______ Mg + ______ O₂ → ______ MgO g) ______ Al + ______ O₂ → ______ Al₂O₃
a) 2, 2, 1 b) 1, 1, 2 c) 2, 1, 2, 1 d) 2,2,1 e) 1,3,2 f) 2,1,2 g) 4,3,2 Balancing a simple equation is usually done by trial and error. However, to help in this process you should first identify what atoms are not balanced. For example, let's start with this equation: H2 + O2 → H2O On the reactant side there are 2 hydrogen and 2 oxygen atoms, on the product side there are 2 hydrogens and 1 oxygen. The number of oxygen atoms is not balanced. Since we need 2 oxygen atoms on the product side and each H2O molecule only contains 1 oxygen atom, we place a 2 in front of the H2O: H2 + O2 → 2H2O However, this causes the hydrogen to become unbalanced. To fix this, we place a 2 in front of the hydrogen on the left side: 2H2 + O2 → 2H2O
Lewis structures or electron dot formulas can be drawn for atoms exhibiting covalent bonding. The exercises below will follow the five steps for drawing Lewis structures for covalent bonds demonstrated in Example 4.11. The questions pertain to water (H2O) where each H is connected to the O. STEPS:
a) How many atoms of each kind are in the molecule? b) Use the bonding pattern described above to draw the initial structure. c) Determine the total number of valence-shell electrons contained in the atoms of the molecule. d) Put one pair of electrons between each bonded pair of atoms. How many valence shell electrons remain? e) Use the remaining electrons to complete the octets of all atoms in the structure. Remember, hydrogen atoms only require 1 pair of electrons to complete their valence shell.
Many important reactions occur when compounds are dissolved in water. When an ionic compound dissolves in water, it dissociates (breaks apart) into its individual (+) and (-) charged parts. In a total ionic equation, all soluble ionic compounds are represented by the ions they form in solution followed by an (aq) symbol. (aq) means aqueous solution, or the ions are dissolved in water. The following ionic compounds are written using their correct formulas. Consider the compounds to be water soluble and write the ionic formulas for the ions that would be formed if the compounds were dissolved in water. Remember, the first element in an ionic compound is the metal and will have a (+) charge. If it is in Group IA (1A) on the periodic table, it will have a 1+ charge. If it is in Group IIA (2A), it will have a 2+ charge. If the metal is aluminum (Al), it will have a 3+ charge. You will have to calculate the charge on any other metals. (See chapter 4, question #16 in this tutor for a review). The second element is the nonmetal and will have a (-) charge. If the second element is N or P, it will have a 3- charge. If it is in Group VIA (6A) of the periodic table, it will have a 2- charge. If it is in Group VIIA (7A), it will have a 1- charge. If there is more than one element in the second part of the compound, it is a polyatomic group and you will have to refer to Table 4.7 on pg. 121 in your textbook to find out the charge. Also, remember that the total number of (+) charges must equal the number of (-) charges in the compound. For a more in depth review of ionic charges, see Sections 4.2 - 4.4 in this tutor. a) KI b) Pb(NO3)2 c) KOH d) BaCO3
a) K+ (aq), I- (aq); K is in group I, and I is in group VII. B) Pb2+(aq), 2 NO3-(aq); each NO3- has a -1 charge so Pb must be 2+. C) K+(aq), OH-(aq); K is in group I, and has a +1 charge so the OH must be -1. D) Ba2+(aq), CO32-(aq); Ba is in group II and so has a 2+ charge, and the CO32- must have a 2- charge to balance the 2+ of Ba.
identify each of the following reactions as decomposition, combination, single-replacement, or double replacement. a) 4Fe + 3O₂ → 2Fe₂O₃ b) NaCl + AgNO₃ → NaNO₃ + AgCl c) 2Al + 3Ag₂S → Al₂S₃ + 6Ag d) H₂CO₃ → H₂O + CO₂
a) combination b) double replacement c) single replacement d) decomposition
