Estimate how many feet by assuming that the sand grains are roughly cube-shaped, each one with an edge length of 0.10 mm. texas has a land area of 268,601 square miles.

solution:

its simple volume of 1 sand grain = (0.10 mm) ³ = 0.001 mm³

1 mole sand x (6.02214x10^23 grains / mole) x (0.001 mm³ / grain) = 6.02214x10^20 mm³

268,601 mi² x (5280 ft / mi) ² x (12 in / ft) ² x (2.54 cm / in) ² x (10 mm / 1 cm) ² = 6.95673x10^17 mm²

V = height x area

height = V / A = 6.02214x10^20 mm³ / 6.95673x10^17 mm² = 865.657 mm

finally ...

865.657 mm x (1 cm / 10 mm) x (1 in / 2.54 cm) x (1 ft / 12 in) = 2.84008 ft ... 6 sig figs.