Lab Exam 2
Where are the valence electrons in an atom?
The valence electrons are located in the outermost occupied shell of an atom.
Calculate the simplest formula for the following compound: b. 0.080 mole of Ba, 0.080 of S, 0.320 mole of O
To solve: Take the smallest unit and divide it by each = .080<.320 1) Divide .080 mol of Ba by 0.080 = 1 2) Divide .080 mol of S by .080 = 1 3) Divide 0.320 mol of O by .080 = 4 4) Write the formula: BaSO4
How does the number of bonded atoms around a central atom determine its shape? Include examples in your answer.
We can look at the VSEPR theory to determine its shape. It indicates the bond angles and lone pairs move as far as possible. It is from a 3D perspective. In example picture, you can tell it is bent because it has angles of 120 degrees
A hydrate of CoCl2 with a mass of 6.00 g is heated strongly. After cooling, the mass of the anhydrate is 3.27 g. b. What is the % water in the hydrate?
2.73 g divided by 6.00 g = .455 = 45.5%
Decomposition
2H2O2 yields with Kelvin added? (KI) 2 H2O + 1 O2
Balance this combination reaction: ___ Mg (s) + ___ O2 (g) yields ___MgO (s)
2Mg (s) + 1 O2 (g) yields 2MgO (s)
Write a balanced equation for the reaction of the magnesium and the oxygen (O2), including their physical states
2Mg (s) + O2(g) yields 2MgO (s)
Balance this equation and write what kind of reaction it is: _____ CaCl2 (aq) + ____ Na3PO4 (aq) yields _____ Ca3(PO4)2 (s) + ____ NaCl (aq)
3 CaCl2 + 2 Na3PO4 yields 1 Ca3(PO4)2 + 6NaCl double replacement
Write a balanced equation for each of the following reactions. Write the correct formulas of the reactants and products and the states of each. Iron and oxygen (O2) gas react to form iron (III) oxide.
4 Fe (s) + 3 O2 (g) yields 2Fe2O3 (s)
A hydrate of CoCl2 with a mass of 6.00 g is heated strongly. After cooling, the mass of the anhydrate is 3.27 g. a. How many grams of H20 were lost from the hydrate?
6.00 - 3.27 = 2.73 g
What is included in a chemical equation?
A chemical equation includes reactants and products. Atoms in the reactants are rearranged to produce new combinations of atoms in the products. Reactants are written on the left, and products on the right. (Reactants yield Products)
How does a hydrate differ from an anhydrate?
A hydrate contains water molecules in it's structure, but an anhydrate is the substance that remains when the water is removed from a hydrate.
Why are electrons shared in molecular compounds?
A molecular compound contains 2 or more nonmetals that form covalent bonds because nonmetals have high ionization energies, valence electrons are shared by nonmetal atoms to achieve stability.
What are polyatomic ions?
A polyatomic ion is a charged particle with two or more atoms. Most consist of a nonmetal such as phosphorus, sulfur, carbon, or nitrogen covalently bonded to oxygen atoms.
Single replacement
Zn + CuSO4 yields Cu + ZnSO4 (balanced)
What evidence of a chemical reaction might you see in the following cases? Refer to Table 1. a. dropping an Alka-Seltzer tablet into a glass of water b. bleaching a stain c. burning a match d. rusting of an iron nail
a. bubbling (formation of a gas) b. change in color c. heat produced & change in color d. change in color & formation of a solid
Know the formula, positive and negative ions, and the name of the ionic compounds. a. iron (III) chloride b. zinc oxide
a. iron (III) chloride positive ion: Fe^3+ negative ion: Cl^- formula: FeCl3 b. zinc oxide positive ion: Zn^2+ negative ion: O^-2 formula: Zn2O2 = ZnO
Know the name, formula, positive and negative ions of the ionic compounds with polyatomic ions. a. potassium carbonate b. chromium (III) hydroxide c. MgSO3 d. Al(NO3)3
a. positive ion: K^+ negative ion: CO3^-2 formula: K2CO3 b. positive ion: Cr^+3 negative ion: OH^- formula: Cr(OH)3 c. positive ion: Mg^+2 negative ion: SO3^-2 name: magnesium sulfate d. positive ion: Al^3+ negative ion: NO3^-1 name: aluminum nitrate
Know the formula, positive, and negative ions of ionic compounds. a. K2S b. BaF2
a. positive ion: K^+ negative ion: s^2- name: potassium sulfide b. positive ion: Ba^2+ negative ion: F^+ name: barium fluoride
How does a combination reaction differ from a decomposition reaction?
combination: elements or simple compounds form a complex product (elements come together) decomposition: a reacting substance is split into simpler substance (compounds come apart)
Be able to write the formula of a molecular compound and be able to write one from written form. EX:
dinitrogen pentaoxide = N2O5 IF7 = iodine heptafluoride
A hydrate of CoCl2 with a mass of 6.00 g is heated strongly. After cooling, the mass of the anhydrate is 3.27 g. c. What is the formula of the CoCl2 hydrate?
CoCl2 * (6H20)
A hydrate of CoCl2 with a mass of 6.00 g is heated strongly. After cooling, the mass of the anhydrate is 3.27 g. d. Write the equation for the dehydration of CoCl2 hydrate.
CoCl2 * H20 yields CoCl2 + H20
Know the element, atomic number, electron configuration, electron-dot symbol, loss or gain of electrons, electron configuration, ionic charge, symbol of ion, name of ion
Ex. - Nitrogen, atomic number - 7, electron configuration - 2,5, loss or gain of electrons: gains 3, electron configuration of ion: 2,8, ionic charge is 3-, symbol of nitrogen = N^3- , name of ion: nitride
Know the types of chemical reactions and how to balance
Examples are shown below.
How do the names of molecular compounds differ from the names of ionic compounds?
Ionic: Cation is named first followed by the anion. If it's an ionic compound with a transition metal, there are more than one possible ion. Molecular - named with the least electronegative ion first + prefixes are given to both ions to indicate number of atoms in each element. The 2nd ion ends in "ide".
How are positive and negative ions formed?
Ions are formed when an atom loses or gains an electron. A positive ion is formed when element loses 1 or more electrons. A negative ion is formed when an element gains 1 or more electrons.
What is meant by the simplest formula of a compound?
It means the lowest whole number ratio of the atoms in a formula.
Look at the table in part F of the lab or the picture attached. Be able to take a formula, draw its electron dot formula, locate the # of electron groups, electron group arrangement, number of bonded atoms, shape, and determine if it is polar or nonpolar.
It's part F on the first lab.
Know the formula, positive, and negative ions of ionic compounds.
Lithium iodide: positive ion: Li^+ Negative ion: I^- Formula: LiI Aluminum Oxide positive ion: Al^3+ negative ion: O^2- Formula: Al2O3
Using the rules for writing the formulas of ionic compounds, write the ions of the correct formula for magnesium oxide.
Mg is Mg^+2 O is O^-2 If you do the switcheroo method, it makes it Mg2O2 which simplifies to MgO.
What happens when a hydrate is heated?
The water molecules are removed.
Why are burning candles and rusting nails examples of chemical change?
They undergo one of the four criteria for a chemical change: a. formation of a gas b. formation of a solid c. change of color (rusting nails) d. heat produced or absorbed (candle)
Calculate the simplest formula for the following compound: a. 0.200 mole of Al and .600 mole of Cl
To solve: take the smallest unit and divide it by each = .200<.600 1) Divide .200 mole of Al by .200 = 1 2) Divide .600 mole of Cl by .200 = 3 3) Write formula = AlCl3
Write a balanced equation for each of the following reactions. Write the correct formulas of the reactants and products and the states of each. Liquid pentane (C5H12) and oxygen (O2) gas react to form carbon dioxide and water.
1 C5H12 (l) + 8 O2 (g) yields 5 CO2 (g) + 6 H2O (l)
Combustion equation
1 Na2CO3 + 2 HCl yields 1 CO2 + 1 H2O + 2NaCl
When 2.50 g of copper reacts with oxygen, the copper oxide compound has a mass of 2.81 g. What is the simplest formula of the copper oxide?
1) Subtract the mass of the copper with the mass of the copper oxide compound to find the mass of oxygen. 2.81 g (copper oxide) - 2.50 copper = .310 g of Oxygen 2) Put the grams of copper and grams of oxygen in moles. .310 g O * 1 mol of O / 16.0 g O = 0.019 mol of Oxygen 2.50 g Cu * 1 mole of Cu / 63.6 g Cu = 0.039 mol of Copper 3) Divide the moles by smallest mol. (the moles of O) 0.019 mole of O / 0.019 = 1 mole of O 0.039 mole of Cu / 0.019 = 2 mole of Cu 4) Assemble the formula = Cu2O
Write a balanced equation for each of the following reactions. Write the correct formulas of the reactants and products and the states of each. Sodium and water react to form sodium hydroxide and hydrogen gas (H2).
2 Na (s) + 2 H2O (l) yields 2 NaOH (s) + H2 (g)
