# FAQ

QA number：17740

## QHow to calculate the molar concentration of the solution

A

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

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