Find the number of SiO2 formula units in m = 1.90g of quartz.

formula units = mass/formula unit mass

formula units = 1.90/60.08 =?

0.032

To find the number of SiO2 formula units in 1.90g of quartz, we need to use the concept of molar mass and Avogadro's number.

Step 1: Determine the molar mass of SiO2.
The molar mass of SiO2 can be calculated by adding the atomic masses of silicon (Si) and oxygen (O).

Atomic mass of Si = 28.0855 g/mol
Atomic mass of O = 15.9994 g/mol

Molar mass of SiO2 = (28.0855 g/mol) + 2 * (15.9994 g/mol) = 60.0843 g/mol

Step 2: Convert the given mass of quartz (1.90g) to moles.
Using the molar mass of SiO2 determined in step 1, we can calculate the number of moles of SiO2 in 1.90g of quartz.

Number of moles = Mass of sample / Molar mass
Number of moles = 1.90 g / 60.0843 g/mol

Step 3: Use Avogadro's number to convert moles to formula units.
Avogadro's number (NA) is approximately 6.022 × 10^23 formula units per mole.

Number of formula units = Number of moles * Avogadro's number
Number of formula units = (1.90 g / 60.0843 g/mol) * (6.022 × 10^23 formula units/mol)

Now, you can perform the calculations to find the number of SiO2 formula units in 1.90g of quartz.

To find the number of SiO2 formula units in 1.90g of quartz, we'll need to follow these steps:

1. Determine the molar mass of SiO2:
The molar mass of silicon (Si) is 28.09 g/mol, and the molar mass of oxygen (O) is 16.00 g/mol. Since there are two oxygen atoms in each SiO2 formula unit, the molar mass of SiO2 is calculated as follows:

Molar mass of SiO2 = (Molar mass of Si) + 2 * (Molar mass of O)
Molar mass of SiO2 = 28.09 g/mol + 2 * 16.00 g/mol
Molar mass of SiO2 ≈ 60.09 g/mol

2. Convert the given mass of quartz to moles:
Moles = Mass / Molar mass
Moles = 1.90 g / 60.09 g/mol
Moles ≈ 0.0316 mol

3. Use Avogadro's number to calculate the number of SiO2 formula units:
Number of formula units = Moles * Avogadro's number
Number of formula units = 0.0316 mol * 6.02 × 10^23 formula units/mol
Number of formula units ≈ 1.90 × 10^22 SiO2 formula units

Therefore, there are approximately 1.90 × 10^22 SiO2 formula units in 1.90g of quartz.