For the following reaction between mohr's salt (iron as feso_4(nh_4)_2so_4 6h_2o) and potassium dichromate (dichromate as k_2cr_2o_7), determine the volume (in milliliters) of a 0.230 m solution of mohr's salt that is needed to fully react with 0.0500 l of 0.230 m potassium dichromate. (the reaction is shown in its ionic form in the presence of a strong acid.)
cr_2o_7^2- + 6fe^2+ + 14h^+ rightarrow 2cr^3+ + 6fe^3+ + 7h_2o
mohr's salt volume = ml
for the same reaction, what volume (in milliliters) of 0.230 m potassium dichromate is required to fully react with 0.0500 l of a 0.230 m solution of mohr's salt
potassium dichromate volume = ml

Answer :

Part 1 : The volume (in milliliters) of a 0.230 M solution of Mohr's salt is 8.33 mL.

Part 2 : The volume (in milliliters) of a 0.230 M solution of potassium dichromate required is 300 mL.

Explanation :

Part 1 :

Using neutralization reaction:

where,

are the n-factor, molarity and volume of

are the n-factor, molarity and volume of

We are given:

Putting values in above equation, we get:

Conversion used : (1 L = 1000 mL)

Thus, the volume (in milliliters) of a 0.230 M solution of Mohr's salt is 8.33 mL.

Part 2 :

Using neutralization reaction:

where,

are the n-factor, molarity and volume of

are the n-factor, molarity and volume of

We are given:

Putting values in above equation, we get:

Conversion used : (1 L = 1000 mL)

Thus, the volume (in milliliters) of a 0.230 M solution of potassium dichromate required is 300 mL.

part 1: the half-life of the element is 22 years.

part 2: it will take 132.02 year for the sample to decay from 308.0 g to 4.8125 g.

explanation:

part 1: there are two ways to determine the half life time.

first way: the half life time can be determined directly from its definition as it is the time required for the sample to decay to its half concentration.

from the data the initial concentration was 45.0 g and decayed to its half value (22.5 g) in 22.0 years.

second way: the radio active decay is considered first order reaction so we can use the laws of first order reactions.

k = (1/t) ln (a/a-x), where k is the rate constant of the reaction,

t is the time of the reaction

a is the initial concentration of the reactant

a-x is the remaining concentration at time (t)

a = 45.0 g the initial concentration at t = 0 year.

at t = 22 year, a-x = 22.5 g

then k = (1/22 year) ln (45.0 g/ 22.5 g) = 0.0315 year-1.

the half-life time (t1/2) = ln 2/ k = 0.693/ k =0.693/ 0.0315 = 22 years.

part 2:

using the same law k = (1/t) ln (a/a-x),

using the given data; a = 308.0 g and a-x = 4.8125 g and the calculated k from the part 1 (k = 0.0315 year-1)

t = (1/k) ln (a/a-x) = (1/0.0315) ln (308.0/ 4.8125) = 132.02 years

1. they vary with a higher number because boiling is way hotter than melting