Chemistry, 17.01.2021 04:00 andy6128

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

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Answer from: mollyallen116365

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: $\displaystyle 30 \ g \ SiO_2(\frac{1 \ mol \ SiO_2}{60.09 \ g \ SiO_2})$ Multiply/Divide: $\displaystyle 0.499251 \ mol \ SiO_2$

Step 4: Check

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

0.499251 mol SiO₂ ≈ 0.50 mol SiO₂

Answer from: Harms

$\boxed {\boxed {\sf About \ 0.5 \ moles \ of \ SiO_2}}$

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.

$\frac{60.083 \ g \ SiO_2}{1 \ mol \ SiO_2}$

Multiply by the given number of grams (30)

$30 \ g \ SiO_2 * \frac{60.083 \ g \ SiO_2}{1 \ mol \ SiO_2}$

Flip the fraction so the grams of sand will cancel.

$30 \ g \ SiO_2 *\frac{1 \ mol \ SiO_2}{60.083 \ g \ SiO_2}$

$30 *\frac{1 \ mol \ SiO_2}{60.083 }$

$\frac{30 \ mol \ SiO_2}{60.083 }$

$0.499309289 \ mol \ SiO_2$

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.

$\approx 0.5 \ mol \ SiO_2$

There are about 0.5 moles of SiO₂ in 30 grams.

Answer from: Quest

The answer is ax3. hope this

Answer from: Quest

The law of conservation of mass states that a mass of an object or the amount of matter composed inside an object or thing will not change unless it is added or removed of the matter that is contained in the object itself.

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