Sand: A grain of sand has approximately [tex]1.69 \times 10^*[/tex] moles of [tex]SiO_2[/tex]. How much does a grain of sand weigh in grams? Assume that sand is 100% [tex]SiO_2[/tex].

The calculation for the weight of a grain of sand based on its SiO2 content requires the molar mass of SiO2 and the precise number of moles present. Without the exact number of moles, an accurate weight in grams cannot be determined.

Explanation:

The question seems to suggest a connection between the number of moles in SiO2 (silicon dioxide) and the weight of a grain of sand. However, there seems to be a misunderstanding in the question provided. To compute the weight of a grain of sand in grams based on its silicon dioxide content, we would typically look at the molar mass of SiO2 and the amount of substance in moles.

The molar mass of SiO2 is approximately 60.08 g/mol. If we were to assume the presence of 1.69×10x moles of SiO2 in a grain of sand, the actual number of moles (value of 'x') needs to be clarified to calculate the mass accurately. Without the exact number of moles (x), a precise calculation cannot be provided. Generally, for such a calculation, one would multiply the number of moles of SiO2 by its molar mass (in grams per mole) to find the mass in grams.