7 Chemical Formulas Chemical Bonding Stoichiometry
Chapter 7 Chemical Bonding Stoichiometry COURSE NAME: CHEMISTRY 101
COURSE CODE: 1 2 3 Chemical Formulas 4 5 6 7 Chemical Bonding Ionic
bond Na + Cl Na+ Cl-
Ionic bond is formed when metal (electropositive element) lose
electrons forming positive ion and nonmetal (electronegative
element) gain these electrons forming negative ion.The ionic bond
results from the electrostatic attraction between the positive
(cation) and negative ion (anion). An example of an ionic compound
is NaCl where Na is of low ionization potential and Cl is of high
electron affinity. Thus, an electron is taken up by Cl from Na to
become Cl- and Na then becomes Na+. Electrostatic attraction then
occurs between the two ions to form ionic bond. Na + Cl Na+ Cl- 7 8
Covalent Bond (electron pair bond)
The bond formed when two atoms mutually share their electrons. In
the other words, it is the bond formed by sharing a pair of
electrons by two atoms e.g.H + H HH or (H-H) 9 Thus, the structure
is written as H+ Cl-
When the two atoms are of similar electronegativity the covalent
bond is nonpolar. On the other hand, when the two atoms are of
different electronegativity, the bond is polar covalent bond e.g.
H-Cl ; chlorine atom is more electronegativily and attracts the
bond electrons more strongly than hydrogen. Thus, the structure is
written as H+ Cl- Chlorine carries partial negative charge but the
hydrogen carries partial positive charge. 10 11 Coordination bond
This bond formed when a pair of electrons from one atom is shared
between two atoms. Also it can be defined as the bond formed by the
interaction of two atomic orbitals one is doubly occupied and the
other is empty; the first is called donor and the second is called
acceptor. Donor Acceptor Compound We write simply the product as
H3N+BF3- 12 13 Where A and B are strongly electronegative
atoms
Hydrogen bond The attractive force that binds a hydrogen atom which
is covalently attached with a strongly electronegative atom of a
molecule with another electronegative atom of some other molecule.
Thus the existence of hydrogen bond between A-H and B-H molecules
can be shown as: A-H+ .. B-H+ Where A and B are strongly
electronegative atoms 13 14 Stoichiometry Definition: predicting
the amounts of reactants and/or products that will be involved in a
reaction Must use a balanced reaction Why? Because matter can
neither be created nor destroyed.If you try to use a reaction like:
H2 + O2H2O 14 You will have one oxygen atom that does not get
used
You will have one oxygen atom that does not get used.You have to
take that into consideration otherwise the reaction is not an
accurate description of what is happening Since you are only using
of the O2 molecule: H2 + O2H2O This is the same as: 2 H2 + O2 2 H2O
Coefficients tell you the relative amounts of products and
reactants Coefficients are in units of moles 15 Using the
coefficients we can write mole ratios
Example: N2 + 3 H2 2 NH3 Recall that the coefficient on N2 is 1 but
is not explicitly written in the reaction Coefficients: N2 = 1 H2 =
3 NH3 = 2 Using the coefficients we can write mole ratios 16
Definition: mole ratio gives the relative amounts of reactants and
products
17 MOLE to MOLE Stoichiometry
18 MASS to MASS Stoichiometry
19 You can use this version of the mole map to solve stoichiometry
problems.
20 21 1. Determine the number of moles of aluminum in 0.2154 kg of
Al.
A) x 1023 mol B) x 103 mol C) mol D) mol E) x 10-3 mol 2. How many
phosphorus atoms are there in 2.57 g of P? A)4.79 x 1025 B)1.55 x
1024 C)5.00 x 1022 D)8.30 x 10-2 E)2.57 3. What is the coefficient
for CO2 when the following chemical equation is properly balanced
using the smallest set of whole numbers? C4H10 + O2 ----> CO2 +
H2O A)1 B)4 C)6 D)8 E)12 21 5. Calculate the number of moles of H2O
formed when 0
5. Calculate the number of moles of H2O formed when mole of Ba(OH)2
is treated with mol of HClO3 according to the chemical reaction
shown below. Ba(OH)2 + 2 HClO3 ----> Ba(ClO3)2 + 2 H2O A)1.00
mol B) mol C) mol D) mol E) mol 4. What mass of copper(II) nitrate
would be produced from the complete reaction of 45.6 g of copper,
according to the chemical reaction shown below? Cu + 2 AgNO3
----> Cu(NO3)2 + 2 Ag A)0.72 g B)21.1 g C)98.7 g D)135 g E)187 g
22 6. The limiting reagent is the substance:
A)present in greatest quantity B)limits the number of reagents
present C)determined by the amount of reactants present D)that
determines the maximum amount of possible product 7. One mole of H2
A)contains 6.0 x 1023 H atoms. B)contains 6.0 x 1023 H2 molecules.
C)contains 1 g of H2. D)is equivalent to 6.02 x 1023 g of H2.
E)None of the above. 23 24 8. How many oxygen atoms are present in
5.2 g of O2?
A)5.4 x atoms B)9.8 x 1022 atoms C)2.0 x 1023 atoms D)3.1 x 1024
atoms E)6.3 x 1024 atoms 9. What is the mass of 5.45 x 10-3 mol of
glucose, C6 H12O6? A) g B)982 g C)3.31 x 104 g D) g E)None of the
above. 10. Determine the mass percent of iron in Fe4[Fe(CN)6] 3.
A)45% Fe B)26% Fe C)33% Fe D)58% Fe E)None of the above. 11. When
it is correctly balanced, the correct coefficients for the equation
below are PCl3 + H2O ----> H3PO3 + HCl A)1, 3, 1, 1 B)1, 3, 1, 3
C)1, 1, 1, 3 D)2, 3, 2, 3 24
