Question

Calculate the mass in grams of 1.88 × 10^20 molecules of diarsenic pentaoxide. Enter your answer in scientific notation.

Answer 1

Answer: We can use dimensional analysis to convert 1.88 * 10²⁰ molecules diarsenic pentaoxide to moles of diarsenic pentaoxide, to grams of diarsenic pentaoxide.

Molar mass of diarsenic pentaoxide(As₂O₅): 229.8 g/mol

1 mol of diarsenic pentaoxide: 6.022 * 10²³ molecules

Therefore,

Molar mass of diarsenic pentaoxide = 1 mol of diarsenic pentaoxide

229.8 g/mol = 6.022 * 10²³

Mass of 1.88 * 10²⁰ molecules= molar mass * (1.88 * 10²⁰)/1 mol of diarsenic pentaoxide

Mass of 1.88 * 10²⁰ molecules =  229.8*(1.88 * 10²⁰/6.022 * 10²³)

Mass of 1.88 * 10²⁰ molecules = 0.0716 gm

So, mass in grams of 1.88 * 10²⁰ molecules of diarsenic pentaoxide is 0.0716 gm.