Ascientist is trying to discover information about an unknown metal in a compound. the formula for the compound is believed to be xbr3 where x is the unknown metal. the scientist determined that a 4.735 g sample of this compound contains 4.806×10−2 mol br . calculate the atomic mass of the unknown metal, x .

55.5 g/mol

Explanation:

When the compound dissociates it forms :

XBr₃  →  X⁺ + 3Br⁻

So, 1 mol of the metal is equivalent to 3 mol of Br.

1 mol of X 3 mol of Br

y                 4.806x10⁻² mol

By a simple direct three rule:

3y = 4.806x10⁻²

y = 1.602x10⁻²  mol of X

The mass of Br in the compound is the number of moles multiplied by its atomic mass, which is 80 g/mol

m = 80x4.806x10⁻² =

m = 3.845 g

So, the mass of the metal is the total mass less the Br mass (Lavoiser's law):

mX = 4.735 - 3.845

mX = 0.890 g

The atomic mass of X is the mass dividied by the number of moles:

M = 0.890/(1.602x10⁻² )

M = 55.5 g/mol

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.