Question

How many grams are in 1.25037×10² molecules of H₂O?

a) 36 g
b) 18 g
c) 90 g
d) 180 g

Answer 1

To find the mass in grams of 1.25037×10² molecules of H₂O, we convert molecules to moles using Avogadro's number and then multiply by the molar mass of water. The calculated mass is 0.037378 grams, which is not closely matching any of the given options, suggesting a possible error in the options or the initial number of molecules.

Step-by-step explanation:

To determine how many grams are in 1.25037×10² molecules of H₂O, we must first convert the number of molecules to moles using Avogadro's number (6.022×10²³ molecules/mol). Then, we'll use the molar mass of water (18.015 g/mol) to convert from moles to grams.

1. Number of moles of H₂O = (1.25037×10² molecules) / (6.022×10²³ molecules/mol).
2. Calculate the moles of H₂O.
3. Mass in grams = moles of H₂O × molar mass of H₂O (18.015 g/mol).
4. Calculate the mass in grams.

Now let's calculate.

• Moles of H₂O = 1.25037×10² / 6.022×10²³ ≈ 2.075×10²⁻²² moles.
• Mass in grams = 2.075×10²⁻²² moles × 18.015 g/mol ≈ 0.037378 g.

The mass is much less than the options given (a-d), which are all more than one gram; hence, there might be an error in the provided options or a mistake in the calculation of the number of molecules initially provided.