Liquids in a form of mixture has less weight as compared to sum of all liquid's weight due to release of gases.
The combined weights of several liquids mixed in an open flask be less than the sum of all the weights of the liquids because when the reaction occurs new products are formed and also some gases which releases in the atmosphere.
These gases also contribute in the weight of the product so when it is released the weight of the mixture of liquids are less than the sum of the weights of all liquids so we can conclude that liquids in a form of mixture has less weight as compared to sum of all liquid's weight.
This is because Hybridization of an s orbital with all three p orbitals (px , py, and pz) results in four sp3 hybrid orbitals. sp3 hybrid orbitals are oriented at bond angle of 109.5 degrees from each other. This 109.5 degrees gives an arrangement of tetrahedral geometry