How many moles of sand (SiO2) are in 30 g of sand?

0.50 mol SiO₂

General Formulas and Concepts:

Math

Pre-Algebra

Order of Operations: BPEMDAS

Brackets Parenthesis Exponents Multiplication Division Addition Subtraction Left to Right

Chemistry

Atomic Structure

Reading a Periodic TableUsing Dimensional AnalysisExplanation:

Step 1: Define

30 g SiO₂ (sand)

Step 2: Identify Conversions

Molar Mass of Si - 28.09 g/mol

Molar Mass of O - 16.00 g/mol

Molar Mass of SiO₂ - 28.09 + 2(16.00) = 60.09 g/mol

Step 3: Convert

Set up:                                Multiply/Divide:                  

Step 4: Check

Follow sig figs and round. We are given 2 sig figs.

0.499251 mol SiO₂ ≈ 0.50 mol SiO₂

Explanation:

To convert from grams to moles, we must use the molar mass.

1. Molar Mass

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

2. Calculate Moles

Use the molar mass as ratio.

Multiply by the given number of grams (30)

Flip the fraction so the grams of sand will cancel.

3. Round

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 0.5 moles of SiO₂ in 30 grams.

For cyclohexane compounds drawn in a chair conformation:   -axial bonds are vertical  -equatorial bonds are parallel to two bonds within the ring.  thus, as i assume the chair conformation is drawn:   -the x group is in an axial position, as are the five other vertical bonds.  -three axial bonds are on the top face of the ring  -the other three axial bonds are on the bottom face  the position of the second substituent on each ring carbon is equatorial.  gauche groups must be on an adjacent carbon such as carbon 6 and carbon 2, and also gauche groups are rotated by 60 degrees relative to each other.  drawing the newman projections for c1–c2 and c1–c6 aids in visualizing the groups that are gauche to the y group on c1.  click this link and watch some academic videos that may you more understand the topic 

The answer is the first option just took the test