How many cases of hiv/aids infection exist in the world today?
a. 1.5 million
b. 25 million
c. 33 million
d. 42 million

Asample of radium-226 will decay 1/4 of its original amount after 3200years. what is the half-life of radium-226?

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.

If 90.0 grams of ethane reacted with excess chlorine,how many grams of dicarbon hexachloride would form