Bulk title (T) is a method of concentration of solutions that relates the mass of the solute with the mass of solution. For this reason, it always expresses the quantity of the solute in relation to the solution, that is, whenever we calculate the mass titre, its result refers to the solute in the solution.
The solution mass is the sum of the solute mass (m1) and the mass of solvent (m2).
m = m1 + m2
Bulk Title Formula
The formula used to calculate the bulk title is:
T = m1
m
T = mass titre of the solute
m1 = mass of solute
m = solution mass
T = m1
m1 + m2
m2 = mass of solvent
Bulk Title Unit
In calculations with the mass title, we must always use the masses of solute, solvent and solution in the same unit. So, since it is a relationship between masses, the units are divided; soon, the mass title does not have measurement unit.
Percentage from bulk title
From the title value of a solution, we can calculate the percentage of solute and also of solvent using the following formula:
P = T. 100
P = percentage
T = bulk title
It is noteworthy that we always calculate the percentage from the bulk title. Only the percentage of solute is directly determined. To determine the percentage by mass of the solvent in a solution, it is necessary to subtract from 100 the percentage found for the solute:
Solvent mass percent = 100 - solute mass percent
Examples of Bulk Title Calculations
1st example- (FO-Diamantine-MG) How many grams of water are needed to prepare a 20% by weight solution using 80 g of solute?
a) 400
b) 500
c) 180
d) 320
e) 480
Data provided by the exercise:
Percentage = 20%
Solute mass (m1) = 80g
water mass (m2) = ?
Step 1: turn the given percentage into a title.
P = T. 100
20 = T. 100
T = 20
100
T = 0.2
Step 2: use the data in the formula below to determine the mass of water.
T = m1
m1 + m2
0,2 = 80
80+m2
0,2. (80 + m2) = 80
16 + 0.2m2 = 80
0.2m2 = 80 – 16
m2 = 64
0,2
m2 = 320g
2nd example - (UFMS) Sucrose is a very soluble carbohydrate in water; to saturate 0.5 L of pure water (d = 1.0 g/mL) at a temperature of 20°C, 1000 g of this sugar is needed. Approximately what is the concentration of this solution in percent (m/m)?
a) 50%.
b) 25%.
c) 78%.
d) 67%.
e) 90%.
Data provided by the exercise:
Percentage = ?
Solute mass (m1) = 1000 g
Water flow (V2) = 0.5 L or 500 mL
Water density (d2) = 1 g/ml
Step 1: calculate the mass of the solvent used in preparing the solution from the density formula.
d2 = m2
V2
1 = m2
500
m2 = 500g
Step 2: use the data in the formula below to determine the bulk title.
T = m1
m1 + m2
T = 1000
1000 + 500
T = 1000
1000 + 500
T = 1000
1500
T = 0.67 (approximately)
Step 3: calculate the percentage from the found bulk title.
P = T. 100
P = 0.67. 100
P = 67%
By Me. Diogo Lopes Dias
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/quimica/o-que-titulo-massa.htm
