Me on i'll mark !
oxygen has three isotopes: o16 , o17 , and o18 . in any given sample, 99.757% is o16 , 0.038% is o17 , and 0.205% is o18 . the atomic mass of each is as follows: o16=15.995 amu ; o17=16.999 amu ; o18=17.999 amu .
what is the average atomic mass of oxygen?
a) 15.995 amu
b) 15.999 amu
c) 16.060 amu
d) 16.099 amu

An atom of lithium (li) and an atom of chlorine (cl) engage in a chemical reaction. which correctly describes the structure of the resulting chemical compound? hint: consider the class of each element. the chemical compound will have a network structure. the chemical compound will have triple bonds. the chemical compound will have a ball-and-stick structure. the chemical compound will have double bonds.

The scheme below is from a series of reactions that are part of a synthesis of vitamin a. answer the following questions with reference to this scheme. (i) what is "reagent a"? (ii) draw a step-by-step mechanism which explains the formation of compound c from compound b (iii) which reagents would you use to form compound e from compounds c and d (reagents b and c)? for each reagent suggested above in (ii) explain the role of the reagent in the reaction to (iv) form compound e. you may wish to do this by drawing a mechanism. 1. addition of reagent a но reagent a 2. н,о" thо oh нон-с compound a. compound b. compound c .ch-оh 1. reagent b "сно 2. reagent c сh oh compound e. compound d.

Chromosome 17 is made of over million base pairs.