The density ratio is equal to the molar mass of the substance How do you remember?

The density ratio is equal to the molar mass of the substance How do you remember?

Just remember a formula, PV = NRT. Where p is the pressure, V is the volume, n is the amount of matter, R is a definite number, and t is the temperature

Given the density of water ρ = 1 * 10 ^ 3kg / m ^ 3, the molar mass of water is 1.8 * 10 ^ 3kg / mol
(1) How many water molecules are there in one cubic centimeter of water?
(2) Estimate the diameter of a water molecule
I calculated that it was (1) 3.3 * 10 ^ 17, but the answer was 3.3 * 10 ^ 22

1. The density of water is 1g / cm ^ 3, so the number of water molecules (1 / 18) * 6.02 * 10 ＾ 23 in 1cm ^ 3 water is about 3.34 * 10 ^ 22. The answer is right
Twenty five million water molecules are arranged in a line with a length of 1cm and a diameter of 4 * 10 ^ - 10m

The density of water is 1000kg / M and the molar mass of water is 0.018kg/mol
(1) Ball model v = 4 π R & # 179 / 3 (2) cube model: v = A & # 179; (only one significant digit is required)

The volume of 1mol water is v = m / P = 0.018/1000 = 1.8 * 10 ^ - 5 m ^ 3, then the volume of a water molecule is v = V / Na = 1.8 * 10 ^ - 5 / 6.02 * 10 ^ 27 = 3.0 * 10-33 m ^ 3, and then the diameter can be estimated by two models

At a certain temperature, a certain substance with molar mass m is dissolved in an appropriate amount of water, and a saturated solution with mass concentration C and density p is obtained
The solubility of this substance is?

Let the volume of solution be 1 L, then the mass of solution is p (if the density is g / ml, multiply by 1000), the mass of solute = cm, the mass of water = p-cm, the solubility = 100 × cm / (p-cm) g, (if the density is g / ml, it is 100 × cm / (1000p-cm))