Which type of substance cannot be separated physically? an alloy a mixture heterogeneous pure

When determining the shape of a molecule, it is important to draw a lewis dot structure first in order to see the total number a. electrons within the moleculeb. bonding and unshared pairs around central atomc. unshared pair within the molecule( i really need it )

To find the enthalpy of a reaction in the lab, you measured the of the reactants and the change during the reaction.

How many atomic mass units are equal to 1.672×10−24 g of protons?