write the given data first and SOLVE the problem.GIVEN:❆ Density (d) = 1.292 g/L❆ Volume of Air (v) =  6L❆ Temperature (t) = 20°C = 20 + 273 = 293 KNote:-S.I unit of temperature is 'Kelvin' so we need to convert its value from °C to K . To do that just we need to ADD the +273 with given temperature.❆ Pressure (P) = 755 mm of Hg =  = 0.99 atm ≈ 1 atmNote:-Standard S.I unit of pressure is "atmospheric pressure".But here it is given mm of Hg so we need to divide the given value by 760 to obtain the resultant atm pressure value.SOLUTION:✧ Density = Mass/Volume {Here Volume is given as standard S.T.P so we need to take it value as  22.4 L}1.292 g/L × 22.4 L = Mass  {L and L will get cancelled}Mass = 28.94 grams✧ We need to use the gas formula to find the weight of 6L of airPV = nRTHere,✯ P = Pressure✯ V = Volume✯ n = Number of moles✯ R = Universal Gas constant = 0.0821 is its value ✯ T = temperature1×6 = ×0.0821×2936  =  Weight/28.94 ×25.0556 × 28.94 = weight × 25.055173.64 = Weight × 25.055173.64/25.055 = Weight Weight = 7.218 gramsW ≈ 7.2 gramsHence it weight will be 7.2 grams at 6LTo calculate any values RELATED to ideal gas, Then use ideal gas equation PV = nRT n can ALSO be taken as w /G.M.W Where ✯ P = Pressure✯ V = Volume✯ n = Number of moles✯ R = Universal Gas constant ✯ T = temperatureAlso u need to note the ✯ Mass × Volume = Density With these formulas u can calculate any sum regarding to ideal gases.Hope it helpsThanks for asking:-)