Question

You are using water to dilute small amounts of chemicals in the laboratory, drop by drop. How many drops of water are there in a 1.0L bottle ?

Answer 1

$$V_{drop} = 4/3\pi r^3$$

$$mg=2\pi r\gamma$$

$$m=V_{drop} \rho$$

Where V drop - volume of one drop, m - mass one drop, r - radius of drop, rho - density of water, gamma - surface tension of water.

$$4/3\pi r^3 \rho g= 2\pi r \gamma$$

$$r =( 3\gamma/2g\rho)^{0.5}$$

$$r=0.0033 m$$

$$V_{drop} = 0.15 ml$$

$$Quantity _{drops}= 1000/0.15= 6542$$