Chem- Ch.6
All of the statements regarding redox reactions are true
Alkali metals often behave as reducing agents because they readily lose electrons a reducing agent causes another substance to be reduced halogens usually behave as oxidizing agents because they readily gain electrons metal ions are produced when pure metals are oxidized
Combustion
An exothermic reaction between fuel and an oxidant that produces oxidized products
Precipitation reactions
An insoluble solid precipitate drops out of the solution and separates from the solution. This occurs when anions and cations of two ionic compounds change partners
What occurs in a chemical reaction?
Atoms in reactants are rearranged to form new bonds
Examples of chemical change include:
Bleaching, burning, rusting, fermenting
When the reaction shown is correctly balanced, the coefficients are Li + Br2 → LiBr
2, 1, 2
Which sample contains the largest number of atoms?
2.0 mol CH4
In the reaction shown, how many moles of HCl are needed to react with 2.4 moles of Al? 2 Al + 6 HCl → 2 AlCl3 + 3 H2
2.4 x 6/2 =7.2
How many molecules are present in 3.25 mol of C2H6O?
3.25 x 6.002x10^23 = 1.96x10^24
What is Avogadro's number?
6.022x10^23
What is a physical change?
A change in the state of a substance but does not involve a change in the identity or composition of the substance
What is a chemical change?
A change of one substance into a new substance that has different properties
Which statement concerning the mole is not correct?
A mole of any compound contains one mole of each kind of atom found in that compound
In a double replacement, positive ions in reacting compounds switch places
AB + CD --> AD+ CB
Acid base neutralization
Acid reacts with base to yield water and an ionic compound called a salt
How many moles are present in 100.0 g of Al?
Converting grams to moles
Example: What is the mass of 3.987 mol of Al?
Converting moles to grams
In the reaction shown, ________ is the oxidizing agent because it ________
CuCl2; gets reduced
Which combination of ions most likely to produce a precipitate?
FE3+ OH-
True/ false: One mole of methane, CH4, contains the same number of atoms as one mole of carbon dioxide, CO2.
False
True/ false: when a substance is oxidized its charge (or oxidation number) decreases
False
Which reaction is an example of both a precipitation and a neutralization?
H2SO4 (aq) + Ba(OH)2 (aq) → BaSO4 (s) + 2 H2O (l)
What is Oxidation?
Loss of electrons, but if electrons are added to right side of equation, it is also oxidation. Oxidation will always occur on the right side of equation.
Which combination of ions are least likely to produce a precipitate?
MG2+ C2H3O2-
How do you find average mass?
Add all masses of each substance together. Ex: CHCl3 1 C = 12.01 1 H = 1.008 3 Cl = 3 x 35.45 = 106.35 12.01 + 1.008 + 106.35 = 119.37 The average mass of CHCl3 is 119.37
The number of grams in 7.00 moles of N2
N=14 14x2=28 28x7=196
Can subscripts be changed when balancing a chemical equation
NO
Which of the following is always a spectator ion in a chemical reaction?
Na+
The number of grams in 0.350 mol of Na is
Na= 23 (round up) 0.350x23=8.05
Which statement concerning the mole concept is not true?
One mole of any compound contains one mole of atoms
Is loss of hydrogen oxidation or reduction?
Oxidation
What is Reduction?
Reduced charge. Addition of electrons on left of equation is also reduction. Reduction will always occur on the left of equation
Is a gain of hydrogen oxidation or reduction?
Reduction
The Law of Conservation of Mass is
The scientific principle which is the basis for balancing chemical equations
Which combinations are least likely to produce a precipitate?
Those that are both soluble
Which combinations are most likely to produce a precipitate?
Those that are insoluble and soluble in water
True/ False: For every mole of a substance, you have 6.022x10^23 number of atoms
True
How many moles of oxygen react with hydrogen to produce 27.6 mol of H2O? 2H2+O2⟶2H2O
Use the stoichiometric ratio: 1mol O2/ 2mol H2O
Consider the reaction shown and identify the statement that is not true CaCO3 (s) 825C--> CaO (s) + CO2 (g)
Water must be present for this reaction to occur
For an equation needing to know the amount of grams, the conversion order should be
grams --> moles --> moles --> grams
When a solution of iron(III) nitrate is mixed with a solution of sodium hydroxide, a rust colored precipitate forms. This precipitate is probably
iron(III) hydroxide
When a substance loses electrons it is ________; the substance itself is acting as a(an) ________ agent
oxidized, reducing
The element chlorine is very reactive as a(an) ________ agent because it readily ________ electrons to form the chloride ion
oxidizing, gains
The oxidation number of iron in the compound FeBr3 is?
+3
The oxidation number of chlorine in the compound FeCl3 is
-1
In the balanced reaction shown, the mole ratio of Fe2S3 to O2 is Fe2S3 + 4 O2 → 2 FeO + 3 SO2
1 to 4
How many grams are there in 1.50 × 1025 atoms of carbon?
We know that one mole of carbon, has a mass of 12 grams (look on the periodic table) We also know that for every mole we have 6.022x10^23 atoms Therefore to find atoms we would set up an equation like this:
Do ionic equations break down to net ionic equations?
Yes
What is a spectator ion?
an ion that appears on both sides of an equation and is not directly involved in the reaction, does not change
Example:
calculating kilograms of glucose to moles