Which of the following is an observation and not an inference?
a.
a cup with steam coming from it will be hot to the touch.
b.
dark clouds in the sky will mean rain later in the afternoon.
c.
bubbles form when two chemicals are mixed together.
d.
a plastic bag moving along the ground is being pushed by the wind.

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 dependant variable is spilled water

the independent is the heat