Answer:
Explanation:
To convert from grams to moles, we must use the molar mass.
<u>1. Molar Mass </u>
Use the Periodic Table to find the masses of the individual elements (silicon and oxygen) in sand.
- Silicon (Si): 28.085 g/mol
- Oxygen (O): 15.999 g/mol
Examine the formula for sand: SiO₂. There is a subscript of 2 after oxygen, so there must be 2 oxygen atoms. Multiply oxygen's mass by 2 and add silicon's mass to find the molar mass of sand.
- SiO₂: 2(15.999 g/mol) + 28.085 g/mol= g/mol
<u>2. Calculate Moles </u>
Use the molar mass as ratio.
Multiply by the given number of grams (30)
Flip the fraction so the grams of sand will cancel.
<u>3. Round </u>
The original measurement of grams has 1 signfiicant figure. We must round our answer to 1 sig fig.
For the answer we found, that is the tenth place. The 9 in the hundredth tells us to round the 4 to a 5.
There are about <u>0.5 moles</u> of SiO₂ in 30 grams.