Asample of gold (au) has a mass of 35.12 g.
a.
calculate the number of moles of gold (au) in the sample. show your work.

b.
calculate the number of atoms of gold (au) in the sample. show your work

a. 0.18 mol

b. 1.084 x 10²³ atoms

Explanation:

Data Given:

mass of gold (Au) = 35.12 g

a. number of moles of gold (Au) = ?

b. number of atoms of gold (Au) =?

Solution:

Part a:

To find number of moles following formula will be used

                no. of moles = mass in grams / molar mass . . . . . . (1)

molar mass of gold (Au) = 197 g/mol

put values in equation 1

                 no. of moles = 35.12 g / 197 g/mol

                 no. of moles = 0.18 mol

so. number of moles of Au = 0.18 mol

Part b:

To find number of atoms following formula will be used

                no. of moles = no. of atoms / Avogadro's number

Rearrange the above equation

no. of atoms = no. of moles x Avogadro's number . . . . . . . (2)

Avogadro's number = 6.022 x 10²³ atoms /mol

put values in equation 1

                 no. of atoms =  0.18 mol x 6.022 x 10²³

                 no. of atoms = 1.084 x 10²³

so.

number of atoms of Au = 1.084 x 10²³ atoms

Explanation:

Given data:

Mass of gold = 35.12 g

Number of moles of gold = ?

Number of atoms of gold = ?

Solution:

A) Number of moles:

Formula:

Number of moles = mass/ molar mass

Molar mass of gold = 197 g/mol

Number of moles = 35.12 g/ 197 g/mol

Number of moles = 0.18 mol

B) Number of atoms:

The given problem will solve by using Avogadro number.

It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance.

The number 6.022 × 10²³ is called Avogadro number .

One mole =  6.022 × 10²³ atoms

0.18 mol ×  6.022 × 10²³ atoms / 1mol

1.084  × 10²³ atoms of gold

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.