Answer:
The concentration of the unknown acid (HA) is 0.434M
The molar mass of HA is 13.3g/mole
Explanation:
DETERMINATION OF MOLARITY OF THE UNKNOWN ACID
CaVa/CbVb = Na/Nb
From the equation of reaction and at equivalence point, Na = Nb = 1
Therefore, CaVa = CbVb
Va (volume of acid solution) = 20mL = 20/1000 = 0.2L
Cb (concentration of KOH) = 0.715M
Vb (volume of KOH) = 12.15mL
Ca (concentration of acid) = CbVb/Va
Ca = 0.715M × 12.15mL/20mL = 0.434M
DETERMINATION OF MOLAR MASS OF HA
Number of moles of acid = concentration of acid × volume of acid solution in liters = 0.434 × 0.2 = 0.0868mole
Molar mass of HA = mass/number of moles = 1.153g/0.0868mole = 13.3g/mole
Answer:
149.79
Explanation:
Formula
Joules = m * c * delta (t)
Givens
J = 28242
m = ?
c = 4.19
Δt = 63 - 18 = 45
Solution
28242 = m * 4.19 * 45
28242 = m * 188.55
m = 28242 / 188.55
m = 149.79
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%
