Calculate the molecular weight when a gas at 25.0 ∘c and 752 mmhg has a density of 1.053 g/l .

26.0 g/mol The ideal gas law is PV = nRT where P = pressure V = volume n = amount of substance R = ideal gas constant (8.3144598 (L kPa)/(K mol) ) T = absolute temperature Solving for n, gives PV = nRT PV/RT = n Convert pressure from mmHg to kPa 752 mmHg = 752 * 0.133322387415 = 100.2584353 kPa Convert temperature from C to K 25.0 C = 25.0 C + 273.15 = 298.15 K Volume will be 1 liter. Substitute known values into equation solving n PV/RT = n (100.2584353 kPa * 1 L)/(8.3144598 (L kPa)/(K mol) 298.15 K) = n (100.2584353 kPa L)/(2478.956189 (L kPa)/mol) = n 0.040443811 mol = n So we know we have 0.040443811 moles of the unknown gas. Now just divide the mass of the gas by the number of moles. 1.053 g / 0.040443811 mol = 26.03612214 g/mol Rounding to 3 significant figures give 26.0 g/mol

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