A student was using the periodic table to organize elements based on their ionization energy from lowest to highest. At the end of the class period, the student left one of the 4 spaces blank. It looked like this: Ba, Co, , He.

Which of the following elements would best fit into this model?

A.
N would go into the blank because it fits the diagonal trend that points towards the upper right.

B.
Se would go into the blank because it fits the diagonal trend that points towards lower left.

C.
Kr would go into the blank because it is a noble gas and has a lower ionization energy than helium but higher than cobalt.

D.
Sb would go into the blank because it has more energy levels than cobalt which gives it a higher ionization energy than cobalt but less than helium.

The diagram shows the structures of horse and cat forelimbs. what does the diagram suggest about the evolutionary relationship between these two mammals? a. they have homologous structures, indicating a common ancestor. b. they have analogous structures, indicating a common ancestor. c. they have homologous structures, indicating that they do not have a common ancestor. d. they have analogous structures, indicating that they do not have a common ancestor.

What is the relation between concentration of reactants and the rate of chemical reaction?

Straightforward questions answered in the powerpoint slidesreaction: heating the starting materials under refluxwhat does it mean to heat under reflux? why do we choose water as the reflux solvent? what are boiling chips used for? why do we put a condenser on top of the reaction? why do we add heat and let the reaction stir for 30 minutes? why do we add sulfuric acid to the reaction after it cools as opposed to when it’s still hot? separation: filtration of precipitatewhy don’t we do an aqueous and organic extraction in the separatory funnel? why do you rinse the salicylic acid on the filter with ice cold water? purification: recrystallization of salicylic acid (no hot filtration needed)what is the difference in the amount of room temperature water vs. boiling water needed to dissolve the salicylic acid (assume a 1.2 gram yield of salicylic acid)? remember, in the lab if you need x ml of boiling water to dissolve a solid, then you should add a little more (definitely no more than 1.5 times the theoretical amount) to ensure it doesn’t recrystallize prematurely.analysis: melting point of salicylic acidwhat can you conclude if the melting point of the salicylic acid you just synthesized is 152-155oc and the 1: 1 mix of your product and “synthetic” salicylic acid is 151-154oc?