How do I determine the number of moles for the substance: 3.5 x 10^23 molecules H2O?

1 mol of anything has 6.02 x 10^23 molecules of (in this case) H2O. This must be close to a 0.5 mol but you need to do the exact arithmetic.

How do I determine the number of grams for the following Substance? 7.8 mol ZnSo4.

grams = mols x molar mass

How do I determine the number of grams for the following Substance? 7.8 mol ZnSo4

To determine the number of moles for a given substance, such as 3.5 x 10^23 molecules of H2O, you need to use Avogadro's number, which is 6.022 x 10^23 particles per mole. Here's how you can calculate the number of moles:

Step 1: Identify the given quantity. In this case, it is 3.5 x 10^23 molecules of H2O.

Step 2: Recognize that Avogadro's number tells you the number of particles per mole. Since 1 mole of any substance contains 6.022 x 10^23 particles, you use this ratio to convert between particles and moles.

Step 3: Set up a proportion using the given information and Avogadro's number. The proportion is as follows:
(3.5 x 10^23 molecules of H2O) / (6.022 x 10^23 molecules per mole)

Step 4: Cancel out the units and calculate the answer.
(3.5 x 10^23) / (6.022 x 10^23) ≈ 0.581 moles (rounded to three decimal places)

Therefore, 3.5 x 10^23 molecules of H2O is approximately equal to 0.581 moles of H2O.