The recommended dally allowance (RDA) of selenium in your diet is 55 micrograms. how many atoms of selenium is this? 4.19 x 10^17 atoms Se

4.2 × 10¹⁷ atoms of Se

Explanation:

Step 1: Convert the mass to grams

We will use the conversion factor 1 g = 10⁶ μg.

55 μg × 1 g/10⁶ μg = 5.5 × 10⁻⁵ g

Step 2: Calculate the moles corresponding to 5.5 × 10⁻⁵ g of Se

The molar mass of Se is 78.96 g/mol.

5.5 × 10⁻⁵ g × 1 mol/78.96 g = 7.0 × 10⁻⁷ mol

Step 3: Calculate the atoms in 7.0 × 10⁻⁷ moles of Se

We will use Avogadro's number: there are 6.02 × 10²³ atoms of Se in 1 mole of Se.

7.0 × 10⁻⁷ mol × 6.02 × 10²³ atom/1 mol = 4.2 × 10¹⁷ atom

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.