194
Stoichiometry III Calculations Based on Concentrations of Solutions
SOLUTION:
We are given the initial and final concentrations of the two solutions, along with the
final volume Therefore,
(, 8 o
\
(V liters) = (2 00 liters) 3 00
liter /
\
liter
To prepare the solution measure out 333 ml of 1 8 0 M H 2 SO 4 and dilute it to 2 00
liters in a volumetric flask Shake well for uniformity Because the interaction of
concentrated H 2 SO 4 with H 2 O evolves mm h heat and can cause hazardous splattering, it is better to do a partial dilution with about one liter of water first in a
beaker Then, after cooling, transfer the contents to the volumetric flask, and
complete the dilution The final dilution to the mark must be made with the
solution at room temperature
PREPARATIVE REACTIONS
Solutions often are involved in reactions used to prepare compounds or to
perform chemical analyses In either case, you will be faced with stoichiometncal calculations similar to those in Chapters 10 and 12, but you must also
consider the concentrations and volumes of the solutions that are used We shall
use the "three simple steps" as outlined on p 173
PROBLEM:
Cupnc nitrate is prepared by dissolving a weighed amount of copper metal in a
nitric acid solution
3Cu + 8HN0 3 -* 3Cu(NO 3 ) 2 + 2ND + 4H 2 O
3Cu + 2NO, + 8H+^ 3Cu
2+ + 2ND + 4H 2 O
What volume of 6 00 M HNO 3 should be used to prepare 10 0 g of Cu(NO 3 V
SOLUTION:
1 From the given weight of Cu(NO 3 ) 2 , calculate the moles of Cu(NO 3 ) 2 that are
given (to prepare)
moles of Cu(NO 3 ) 2 given = —
10 ° §
= o 0533 mole Cu(NO 3 ) 2
187 5 g Cu(NO 3 ) 2
mole Cu(NO 3 ) 2
2 From the given number of moles of Cu(NO 3 ) 2 , calculate the moles of HNO 3
required The chemical equation shows that 8 moles of HNO 3 are required for 3
moles of Cu(NO 3 ) 2 Therefore
Stoichiometry III Calculations Based on Concentrations of Solutions
SOLUTION:
We are given the initial and final concentrations of the two solutions, along with the
final volume Therefore,
(, 8 o
\
(V liters) = (2 00 liters) 3 00
liter /
\
liter
To prepare the solution measure out 333 ml of 1 8 0 M H 2 SO 4 and dilute it to 2 00
liters in a volumetric flask Shake well for uniformity Because the interaction of
concentrated H 2 SO 4 with H 2 O evolves mm h heat and can cause hazardous splattering, it is better to do a partial dilution with about one liter of water first in a
beaker Then, after cooling, transfer the contents to the volumetric flask, and
complete the dilution The final dilution to the mark must be made with the
solution at room temperature
PREPARATIVE REACTIONS
Solutions often are involved in reactions used to prepare compounds or to
perform chemical analyses In either case, you will be faced with stoichiometncal calculations similar to those in Chapters 10 and 12, but you must also
consider the concentrations and volumes of the solutions that are used We shall
use the "three simple steps" as outlined on p 173
PROBLEM:
Cupnc nitrate is prepared by dissolving a weighed amount of copper metal in a
nitric acid solution
3Cu + 8HN0 3 -* 3Cu(NO 3 ) 2 + 2ND + 4H 2 O
3Cu + 2NO, + 8H+^ 3Cu
2+ + 2ND + 4H 2 O
What volume of 6 00 M HNO 3 should be used to prepare 10 0 g of Cu(NO 3 V
SOLUTION:
1 From the given weight of Cu(NO 3 ) 2 , calculate the moles of Cu(NO 3 ) 2 that are
given (to prepare)
moles of Cu(NO 3 ) 2 given = —
10 ° §
= o 0533 mole Cu(NO 3 ) 2
187 5 g Cu(NO 3 ) 2
mole Cu(NO 3 ) 2
2 From the given number of moles of Cu(NO 3 ) 2 , calculate the moles of HNO 3
required The chemical equation shows that 8 moles of HNO 3 are required for 3
moles of Cu(NO 3 ) 2 Therefore