(2) a base because they accept H+ ions. NH3 is the conjugate base of NH4+.
Percentage recovery gives us an idea of the amount of pure substance recovered after the chemical reaction. Percentage recovery can be more than 100 % or less than 100 %. Usually, in any experiment performed the weight percentage recovery will be less than 100. Percent recovery values greater than 100 show that the recovered compound is contaminated.
Amount of acetaminophen initially taken = 350 mg
Amount of acetaminophen obtained after recovery =185 mg

= 
= 52.9%
Convection: the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat.
hope that helps :)
Answer:
In the Lewis structure of P4 there are 6 bonding pairs and 4 lone pairs of electrons.
Explanation:
The structure of tetrahedral molecule of P4 is provided below.
Each phosphorus atom has 5 valence electrons out of which 3 electrons involve in bonding and the rest 2 electrons exist as a lone pair that does not involve in bonding.Hence each phosphorus atom has one lone pair.In P4 molecule there are phosphorus atoms and hence 4 lone pairs in total.
As you can see in the figure, each phosphorus atom is bonded to the other three atoms.A bond is formed when two atoms share one electron each and the pair is called bonding pair.
From the figure we can see that there are 6 bonds in total.Each bond consist of one bonding pair of electrons and hence in total there are 6 bonding pairs of electrons.
Hence in a P4 molecule there are six bonding pairs and 4 lone pairs of electrons.