Question

I need Chemistry help (Connections Unit 6 Lesson 3)

1. A sample of gold (Au) has a mass of 35.12 g.
a. Calculate the number of moles of gold (Au) in the sample and record in
Table 1. Show your work.
b. Calculate the number of atoms of gold (Au) in the sample and record
in Table 1. Show your work.
2. A sample of table sugar (sucrose, C12H22O11) has a mass of 1.202 g.
a. Calculate the number of moles of C12H22O11 contained in the sample
and record in Table 1. Show your work.

Answer 1

1) Number of moles = mass of Au/ molar mass of Au
Mass = 35.12g and molar mass = 196.699.
Number of moles = 35.12/196.699 = 0.178

2) The number of atoms or molecules in one mole of a substance, equal to 6.023 * 10^23.
Hence it follows there are 6.0233 * 10^23 * 0.178 = 1.0702 * 10^23 atoms. 3) Number of moles of sucrose = mass/molar mass.
Molar mass of C12H22O11 = (12*2) + (1*22) + (16 * 11) = 24 + 22 + 176 = 222
Number of moles = 1.202/222 = 0.0054

Answer 2

For 1a: The number of moles of gold are 0.178 moles.

For 1b: There are
`1.071* 10^(23)` atoms of gold.

For 2: The number of moles of
`C_(12)H_(22)O_(11)` are 0.0035 moles.

Explanation:

To calculate the number of moles, we use the following formula:

`Moles=\frac{\text{Given mass}}{\text{Molar mass}}` .....(1)

• For 1a:

We are given:

Given mass of Au = 35.12g

Molar mass of Au = 196.97 g/mol

Putting values in equation 1, we get:

`\text{Moles of Gold}=(35.12g)/(196.97g/mol)=0.178moles`

Hence, the number of moles of gold are 0.178 moles.

• For 1b:

To calculate the number of atoms in 0.178 moles of gold, we follow mole concept.

According to mole concept:

1 mole of an element contains
`6.022* 10^(23)` number of atoms.

So, 0.178 moles of gold will contain
`0.178* 6.022* 10^(23)=1.071* 10^(23)` atoms.

Hence, there are
`1.071* 10^(23)` atoms of gold.

• For 2:

We are given:

Given mass of
`C_(12)H_(22)O_(11)` = 1.202g

Molar mass of
`C_(12)H_(22)O_(11)` = 342 g/mol

Putting values in equation 1, we get:

`\text{Moles of }C_(12)H_(22)O_(11)=(1.202g)/(342g/mol)=0.0035moles`

Hence, the number of moles of
`C_(12)H_(22)O_(11)` are 0.0035 moles.