QHow to calculate the molar concentration of the solution
The molar concentration unit [mol/ L (M)] is a conventionally widely used as concentration method. It is the number of moles of target substance (solute) dissolved in 1 liter of solution. Here is how to calculate the concentration.
(Weight of 1 liter solution) x (purity) ÷ molecular weight
[Specific gravity of solution (g/mL) x 1,000 (mL) x Purity (w/w%) /100 ÷ Molecular weight]
For example, let's calculate the molar concentration of 2-mercaptoethanol (HSCH2CH2OH). The necessary information is as follows.
- Specific gravity (or density) = 1.114 g/mL
- Purity (or content) = 100 w/w% (assumed)
- Molecular weight = 78.13
By calculating this value by applying this value to the above equation, you can know the molar concentration.
1.114 g/mL x 1,000mL x 100w/w%/100 ÷ 78.13 = 14.26mol/L
In order to caluculate the concentration like above, it is necessary to know three points of "specific gravity (or density)", "purity (or content)" and "molecular weight". The table below is a quick reference chart of common acid and base concentrations. In acid and alkali, there is a use for "neutralization titration", "normality (N)" is often used.
【Quick reference chart of common acid and base concentrations】
Compound | Molecular formula | Molecular weight | Purity (w/w%) |
Specific gravity (20℃) |
Concentration (mol/L) |
Equivalent | Normality (N) |
---|---|---|---|---|---|---|---|
Hydrochloric acid | HCl | 36.46 | 20% | 1.10 | 6.0 | 1 | 6.0 |
35% | 1.17 | 11.2 | 11.2 | ||||
Nitric acid | HNO3 | 63.01 | 60% | 1.37 | 13.0 | 1 | 13.0 |
65% | 1.39 | 14.3 | 14.3 | ||||
70% | 1.41 | 15.7 | 15.7 | ||||
Sulfate | H2SO4 | 98.08 | 100% | 1.83 | 18.7 | 2 | 37.3 |
Phosphoric acid | H3PO4 | 98.00 | 85% | 1.69 | 14.7 | 3 | 44.0 |
90% | 1.75 | 16.1 | 48.2 | ||||
Acetate | CH3COOH | 60.05 | 100% | 1.05 | 17.5 | 1 | 17.5 |
Perchloric acid | HClO4 | 100.46 | 60% | 1.54 | 9.2 | 1 | 9.2 |
70% | 1.67 | 11.6 | 11.6 | ||||
Hydrogen peroxide water | H2O2 | 34.01 | 30% | 1.11 | 9.8 | - | |
35% | 1.13 | 11.6 | |||||
Ammonia water | NH3 | 17.03 | 25% | 0.91 | 13.4 | 1 | 13.4 |
28% | 0.90 | 14.8 | 14.8 |
【Quick reference of concentration and unit】
●How to express concentration of solution
Expression | Commentary |
---|---|
Weight percent concentration | "g number" of solute in 100g solution. Expressed as w/w%, wt%, and % for density in many cases. |
Volume percent concentration | "m number" of solute in 100m solution. Expressed as v/v% when mixture or solute is liquid. |
Weight versus volume percent concentration | "g number of solute in 100m of solution. Expressed as w/v%. |
Normality | Gram equivalent number of solute in 1L solution. Expressed as N for capacity analysis. |
Volume specific concentration | Concentration indirectly expressed by the volume ratio of diluting the liquid reagent. It is used in JIS and others. Example: Sulfuric acid (1 + 2) → Sulfuric acid is shown diluted with 2 volumes of water. |
Weight ratio concentration | Concentration indirectly expressed by weight ratio at which solid reagent is dissolved. It is used in JIS and others. Example: Sodium chloride (1 + 19) →Dissolved in 19 weight of water with respect to 1 of NaCl. |
Molarity | Mol number of target substance (solute) in 1L of solution. Expressed as mol/ or M. |
●Prefix representing multiple
Express bigness | Express smallness | |||
---|---|---|---|---|
100 =102 | h(Hecto) | 1/100 =10-2 | c(Centi) | %(Percent) |
1000 =103 | k(Kilo) | 1/1000 =10-3 | m(Milli) | ‰(Permili) |
100万 =106 | M(Mega) | 1/100万 =10-6 | μ(Micro) | ppm |
1 Billion =109 | G(Giga) | 1/10Billion =10-9 | n(Nano) | ppb |
1 Trillion =1012 | T(Tera) | 1/1 Trillion =10-12 | p(Pico) | ppt |
1000 Trillion =1015 | p(Peta) | 1/1000 Trillion =10-15 | f(Femto) | ppq |
●ppmConversion table
ppb | ppm | % | mg/g | mg/L |
---|---|---|---|---|
1,000 | 1 | 0.0001 | 0.001 | 1 |
10,000 | 10 | 0.001 | 0.01 | 10 |
100,000 | 100 | 0.01 | 0.1 | 100 |
1,000,000 | 1,000 | 0.1 | 1 | 1,000 |
10,000,000 | 10,000 | 1 | 10 | 10,000 |