If the density of water is 1.00 g/mL at 25°C, calculate the number of water molecules found in 1.50 x 10³ µL of water.

• A. 3.99 x 10²¹ molecules
• B. 5.01 x 10²² molecules
• C. 7.41 x 10²³ molecules
• D. 6.29 x 10²⁴ molecules

Answer: (B)

Verified step by step guidance

1. Convert the volume of water from microliters (µL) to milliliters (mL). Since 1 mL = 1000 µL, divide the given volume by 1000.
2. Use the density of water to find the mass of the water. Multiply the volume in mL by the density (1.00 g/mL) to get the mass in grams.
3. Convert the mass of water to moles. Use the molar mass of water (approximately 18.02 g/mol) and divide the mass by this molar mass to find the number of moles.
4. Calculate the number of water molecules using Avogadro's number (6.022 x 10^23 molecules/mol). Multiply the number of moles by Avogadro's number to find the total number of molecules.
5. Review the calculations to ensure all unit conversions and multiplications are correct, and compare the result with the given options to identify the correct answer.