What is the molarity of water if its density is 1000kg/m3 (Molar mass of water is
18 g/mol)
55.55 moles
45.46 moles
60.0 moles
40.56 moles
The molarity of pure water, given density of 1000 kg/m³ and molar mass of 18 g/mol, is 55.55 M.[web:1][web:2][web:14] This value matches the first option in the multiple-choice question.
Step-by-Step Calculation
Density of 1000 kg/m³ equals 1 g/mL, so 1 L (1000 mL) of water has mass of 1000 g. Number of moles equals mass divided by molar mass: 1000/18 ≈ 55.55 mol.Molarity, defined as moles per liter of solution, is thus 55.55 mol/L or 55.55 M for pure water in 1 L volume.
Option Analysis
- 45.46 moles: Incorrect; possibly from erroneous molar mass around 22 g/mol (1000/22 ≈ 45.45), but water is 18 g/mol.
- 60.0 moles: Incorrect; might stem from approximating molar mass as 16.67 g/mol (1000/16.67 ≈ 60), ignoring hydrogen atoms.
- 40.56 moles: Incorrect; no standard miscalculation fits, perhaps confusing with other solvents or units.
This calculation appears frequently in CSIR NET Life Sciences for solution chemistry concepts in biochemistry and plant physiology contexts. Precise value is 1000/18 = 55.5̅ M at standard conditions.
