Consider the following space-filling models for dry ice, ethanol, and caffeine: What amount (moles) is represented by each of the following samples? a. 1.50 g of dry ice b. \(2.72 \times 10^{21}\) molecules of ethanol c. 20.0 mg of caffeine

We need to calculate the molar mass of dry ice (solid carbon dioxide, CO2), ethanol (C2H5OH), and caffeine (C8H10N4O2). Dry ice (CO2): Molar mass (CO2) = 1 mol * (12.01 g/mol C + 2 * 16.00 g/mol O) = 44.01 g/mol Ethanol (C2H5OH): Molar mass (C2H5OH) = 1 mol * (2 * 12.01 g/mol C + 6 * 1.01 g/mol H + 1 * 16.00 g/mol O) = 46.07 g/mol Caffeine (C8H10N4O2): Molar mass (C8H10N4O2) = 1 mol * (8 * 12.01 g/mol C + 10 * 1.01 g/mol H + 4 * 14.01 g/mol N + 2 * 16.00 g/mol O) = 194.19 g/mol

a. 1.50 g of dry ice To find the moles of dry ice, we divide the given mass by the molar mass of CO2: Moles (CO2) = \(\frac{1.50\, \text{g}}{44.01\, \text{g/mol}}\) = 0.0341 mol b. \(2.72 \times 10^{21}\) molecules of ethanol To find the moles of ethanol, we divide the given number of molecules by Avogadro's number (6.022 x 10^23 molecules/mol): Moles (C2H5OH) = \(\frac{2.72 \times 10^{21}\, \text{molecules}}{6.022 \times 10^{23}\, \text{molecules/mol}}\) = 0.00452 mol c. 20.0 mg of caffeine First, convert the mass of caffeine from mg to g: 20.0 mg = 0.02 g Next, find the moles of caffeine by dividing the given mass by the molar mass of C8H10N4O2: Moles (C8H10N4O2) = \(\frac{0.02\, \text{g}}{194.19\, \text{g/mol}}\) = 0.000103 mol So the amounts of substances in moles are: a. 0.0341 mol of dry ice b. 0.00452 mol of ethanol c. 0.000103 mol of caffeine