2. if 0.64 mole of b is reacted with excess a according to the following reaction:
2a + 7b - 4q - sr
(a) how many moles of the product r are formed?
(b) how many grams of q are formed if its m. w. is 84.0 gram/mole?

1. 1 mole of anything contains 6.022x10^23 pieces  

d  

2. a  

3. c, number  

5. 1.24x10^24atoms / 6.022x10^23atoms/mole = 2moles h2 atoms  

6. fe2br3 mass = 2moles x mass fe + 3 moles x mass br  

molar mass = grams / number of moles = g/mole  

to find moles = g / molar mass  

to find mass = g = molar mass / moles

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).

level 4 to level 2 : ))