PLEASe help I will count you brainless please :) what element is this?

(apex) when a cup of water is dropped, as the cup falls, the water in the cup falls out true or false?

For a research project, a student decided to test the effect of the lead(ii) ion (pb2+) on the ability of salmon eggs to hatch. this ion was obtainable from the water‐soluble salt, lead(ii) nitrate, which the student decided to make by the following reaction. pbo(s) + 2 hno3(aq) → pb(no3)2(aq) + h2o losses of product for various reasons were expected, and a yield of 86.0% was expected. in order to have 5.00 g of product at this yield, how many grams of pbo should be reacted? (assume that sufficient nitric acid, hno3, would be used.)

#20 which type of bond is formed when bases pair in dna? ionic bond covalent bond coordinate bond hydrogen bond