0.50 Molar means 0.50 moles/liter
(.5 moles/liter)/3.5 moles= 1/7 Liters
Two steps by inspection 1 qt = 0.25 gallons, 13.6 g/mL = 13.6 kg/L
0.25 gallon x 3.785411784 L/gallon x 13.6 kg/L x 1 lb/0.45359237 kg = 28.374 lb.
Hope this Helps!
The answer can be explained when you burn something cleanly (with a very hot item) or not. With a candle lots of Carbon dioxide is producted but when using a bunson burner hardly any CO2 is produced.