WGU D425 INTRODUCTION TO
CHEMISTRY ACTUAL EXAM
which element is the least electronegative in this series: Cs, Li, P
& Cl
CS electronegativity increases as you move to the right of the periodic
table and as you move down a group. Cs is least electronegative.
what is the bond angle btwn 2 atoms in a trigonal planar
geometry
120 degrees angle bond
how many atoms are in 14 moles of cadmium (Cd)
8.4 x 10^24 atoms Cd. avogadro's number (6.02 x 10^23) used to
convert the number of moles to atoms
what is the molar mass for C6H12O6?
180.2g/mol. a single carbon atom has a mass 12g/mol. a single
oxygen atom has a mass of 16g/mol, and a single hydrogen atom has
a mass of 1g/mol. add all the carbons, hydrogens and oxygens in the
molecular formula
what is the molar mass for Mg(OH)2
58.32 g/mol a single magnesium atom has a mass of
24.31 g/mol, and a single hydrogen atom has a mass of 1 g/mol
add the mass for magnesium, hydrogen, and oxygen
converting moles to gas volume
4.96 moles of O2. At STP, 1mol = 22.4L
unknown: volumes of O2
calculate: 4.96 mol x 22.4 L/mol=
,111.1 L
converting gas volume to moles
86.5L of H2. At STP, 1 mol= 22.4 L
unknown: volume of H2
Calculate: 86.5L H2 x 1 mol/ 22.4 L H2=
3.86 mol H2
how many moles are in 40.0 grams of water H2O
1 mol of H2O= 18.1 g H2O, convert grams of H2O to moles of
H2O
2.22 mol
how many formula units are in 48.0 grams of NaOH?
7.23 x 10^23. convert grams of NaOH to moles of NaOH, then
convert moles of NaOH to the number of molecules using avogadro's
number
Standard Temperature and Pressure (STP)
exactly 100 kPa of pressure(0.986) and 273 K (0' C)
Percent Compostion by mass
mass %= mass of element / mass of compound x 100
K2O= potassium oxide
potassium2 - 29.1 x 2= 78.2
oxygen= 16.00
78.20 + 16.00= 94.20
78.20/94.20 x 100= potassium
16/94.20 x 100= oxygen
83.01% K
16.99% O
what is the percent composition by mass for N in NH6PO4
,12.18%
what is the percent composition for K in KCN?
60%
what is the mass of 0.750 moles of ZnSO4?
How many molecules are there in 0.435 moles of C6H12O6
What is the molar mass for NH4C2H3O2
What is the percent by mass for Na, P, and O in Na3PO4
What is the volume of 12.54 mol of Kr at STP
what describes molar mass
Ratio btwn mass and moles
balancing chemical equation
Al+O2 react AlO3
2Al+O2/2 = Al2O3
2(2Al+O2=Al2O3)=
4Al/4+2O/6=2Al/4O3/6
When does a chemical reaction occur?
when chemical bonds are formed or broken by atoms colliding
what coefficient needs to be placed in front of the oxygen atom 0n
the products side in order to balance the following equation
KClO3->2KCl+O2
2in front of the K, you get 2KClO3->2KCl+O2. but now you have 6
O atoms on the left. to get 6 O atoms on the right, put a 3 in front of
the O2.
How is an equation balanced?
by comparing the number of each type of atom in the reactant and
products. for an equation to be balanced the number of atoms for each
, element in the reaction and the total charge must be the same for both
the reactants and the products
what is the balanced product of this equation:
Pb(OH)4+H2SO4-> Pb(SO4)2+H2O
Pb(HO)4+2H2SO4->Pb(SO4)2+4H2O
Reactant: Pb=1 O=12 H=8 S=2 Products: Pb=1 O=12 H=8 S=2
if you add a 2 in front of H2SO4 = # of S atoms
if you add a 4 in front of H2O on the product side, you will have an
equal # of oxygen and hydrogen atoms on both sides
What occurs in a decomposition reaction?
one substance splits into two or more simpler substances
synthesis reaction example
A + B --> AB
elements or compounds undergo a reaction and combine to form a
single new substance
what describes a change in state that is associated with the loss of
electrons
oxidation. the loss of electrons by an element and an increase in
oxidation state creates an oxide
redox reactions (oxidation-reduction reactions)
H2+Cl2-> 2HCL
chemical reactions that transfer electrons between reactants
either increase or decrease in order to form a chemical bond with
another atom.
H2 has been oxidized, and Cl2 has been reduced, making this a redox
reaction
CHEMISTRY ACTUAL EXAM
which element is the least electronegative in this series: Cs, Li, P
& Cl
CS electronegativity increases as you move to the right of the periodic
table and as you move down a group. Cs is least electronegative.
what is the bond angle btwn 2 atoms in a trigonal planar
geometry
120 degrees angle bond
how many atoms are in 14 moles of cadmium (Cd)
8.4 x 10^24 atoms Cd. avogadro's number (6.02 x 10^23) used to
convert the number of moles to atoms
what is the molar mass for C6H12O6?
180.2g/mol. a single carbon atom has a mass 12g/mol. a single
oxygen atom has a mass of 16g/mol, and a single hydrogen atom has
a mass of 1g/mol. add all the carbons, hydrogens and oxygens in the
molecular formula
what is the molar mass for Mg(OH)2
58.32 g/mol a single magnesium atom has a mass of
24.31 g/mol, and a single hydrogen atom has a mass of 1 g/mol
add the mass for magnesium, hydrogen, and oxygen
converting moles to gas volume
4.96 moles of O2. At STP, 1mol = 22.4L
unknown: volumes of O2
calculate: 4.96 mol x 22.4 L/mol=
,111.1 L
converting gas volume to moles
86.5L of H2. At STP, 1 mol= 22.4 L
unknown: volume of H2
Calculate: 86.5L H2 x 1 mol/ 22.4 L H2=
3.86 mol H2
how many moles are in 40.0 grams of water H2O
1 mol of H2O= 18.1 g H2O, convert grams of H2O to moles of
H2O
2.22 mol
how many formula units are in 48.0 grams of NaOH?
7.23 x 10^23. convert grams of NaOH to moles of NaOH, then
convert moles of NaOH to the number of molecules using avogadro's
number
Standard Temperature and Pressure (STP)
exactly 100 kPa of pressure(0.986) and 273 K (0' C)
Percent Compostion by mass
mass %= mass of element / mass of compound x 100
K2O= potassium oxide
potassium2 - 29.1 x 2= 78.2
oxygen= 16.00
78.20 + 16.00= 94.20
78.20/94.20 x 100= potassium
16/94.20 x 100= oxygen
83.01% K
16.99% O
what is the percent composition by mass for N in NH6PO4
,12.18%
what is the percent composition for K in KCN?
60%
what is the mass of 0.750 moles of ZnSO4?
How many molecules are there in 0.435 moles of C6H12O6
What is the molar mass for NH4C2H3O2
What is the percent by mass for Na, P, and O in Na3PO4
What is the volume of 12.54 mol of Kr at STP
what describes molar mass
Ratio btwn mass and moles
balancing chemical equation
Al+O2 react AlO3
2Al+O2/2 = Al2O3
2(2Al+O2=Al2O3)=
4Al/4+2O/6=2Al/4O3/6
When does a chemical reaction occur?
when chemical bonds are formed or broken by atoms colliding
what coefficient needs to be placed in front of the oxygen atom 0n
the products side in order to balance the following equation
KClO3->2KCl+O2
2in front of the K, you get 2KClO3->2KCl+O2. but now you have 6
O atoms on the left. to get 6 O atoms on the right, put a 3 in front of
the O2.
How is an equation balanced?
by comparing the number of each type of atom in the reactant and
products. for an equation to be balanced the number of atoms for each
, element in the reaction and the total charge must be the same for both
the reactants and the products
what is the balanced product of this equation:
Pb(OH)4+H2SO4-> Pb(SO4)2+H2O
Pb(HO)4+2H2SO4->Pb(SO4)2+4H2O
Reactant: Pb=1 O=12 H=8 S=2 Products: Pb=1 O=12 H=8 S=2
if you add a 2 in front of H2SO4 = # of S atoms
if you add a 4 in front of H2O on the product side, you will have an
equal # of oxygen and hydrogen atoms on both sides
What occurs in a decomposition reaction?
one substance splits into two or more simpler substances
synthesis reaction example
A + B --> AB
elements or compounds undergo a reaction and combine to form a
single new substance
what describes a change in state that is associated with the loss of
electrons
oxidation. the loss of electrons by an element and an increase in
oxidation state creates an oxide
redox reactions (oxidation-reduction reactions)
H2+Cl2-> 2HCL
chemical reactions that transfer electrons between reactants
either increase or decrease in order to form a chemical bond with
another atom.
H2 has been oxidized, and Cl2 has been reduced, making this a redox
reaction
