How many cobalt atoms are in 345 g of cobalt

Explanation:

To convert from grams to atoms:

1. Convert grams to moles

First, find the molar mass of cobalt using the Periodic Table of Elements.

Next, use this mass as a ratio or fraction.

Multiply the mass of the given sample (345 grams) by this ratio.

Flip the fraction so the grams of Cobalt will cancel each other out when multiplying.

2. Convert moles to atoms

Use Avogadro's Number, which tells us the number of units (in this case atoms) in 1 mole.

Use this number as a ratio or fraction.

Multiply this ratio by the number of moles we found.

The moles of Cobalt will cancel.

3.Round

The original measurement of 345 has 3 significant figures (3, 4, and 5). We must round to 3 sig figs, which is the hundredth place for this measurement.

The 5 in the thousandth place tells us to round the 2 to a 3.

There are about 3.53*10²⁴ atoms of cobalt in 345 grams.

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%