The answer is A: the PH scale
Answer:
Approximately
(note that
.)
Explanation:
The molarity of a solution gives the number of moles of solute in each unit volume of the solution. In this
solution in water,
Let
be the number of moles of the solute in the whole solution. Let
represent the volume of that solution. The formula for the molarity
of that solution is:
.
In this question, the volume of the solution is known to be
. That's
in standard units. What needs to be found is
, the number of moles of
in that solution.
The molar mass (formula mass) of a compound gives the mass of each mole of units of this compound. For example, the molar mass of
is
means that the mass of one mole of
.
For this question,
.
Calculate the molarity of this solution:
.
Note that
(one mole per liter solution) is the same as
.
Answer:
65.4%
Explanation:
The redox reaction is a 1:1:1 reaction because the reagents suffer a double displacement reaction, and the substance that is substituted have the same charge (H+ and Br-), thus, we first need to know which of the reagents is the limiting.
Let's test the 4-nitrobenzaldehyde as the limiting. The mass needed for sodium borohydride (m) is the mass given of 4-nitrobenzaldehyde multiplied by the stoichiometric mass of sodium borohydride divided by the stoichiometric mass of 4-nitrobenzaldehyde. The stoichiometric mass is the number of moles in the stoichiometric representation (1:1:1) multiplied by the molar mass, so:
m = (4.13 * 37.83*1)/(151.12*1)
m = 1.034 g
So, the mass needed of the other reagent is larger than the mass that was given, so, it will be the limiting, and the stoichiometric calculus must be done with it.
The mass of the product that was expected is then:
m = (0.700*153.14*1)/(37.83*1)
m = 2.83 g
The percent yield is the mass that was formed divided by the expected mass, and then multiplied by 100%:
%yield = (1.85/2.83)*100%
%yield = 65.4%