9. In what year does the Russian chemist Dimitri Mendeleev started the development of the periodic table, arranging chemical elements by atomic
mass?
A. 1866
B. 1867
C. 1868
D. 1869

10. How many elements are there in the formula: Ca(OH).
B. 3
C. 7
D. 8

Suppose you got a low yield of benzoin from your benzoin condensation reaction and thus only have 0.300 g of benzoin to use as the starting material for this reaction. how much concentrated nitric acid should you add? (concentrated nitric acid is 15.8 m). write your answer in the form x.xx ml

Which property of a rock remains unchanged by mechanical weathering? a. total surface area b. size and shape c. mineral composition d. sharpness

Consider hydrogen in an excited state n = 5n=5 that emits photons to reach the ground state. there are various possible transitions other than straight to the ground state that can occur; for example, it can drop to the n = 3n=3 state followed by the n = 3n=3 to the ground state transition. which of the possible transitions will result in the emission of a photon in the visible region?