A chemical reaction (signs)
- rusting
- change in base of chemical
- for example lets say u mix two chemicals, and then it becomes a different new chemical (it changed from the inside)
a physical
- a physical reaction is outer looks not inside.
- it changes on the outside, like changing a color
A student walks down a hall I’m pretty sure
<u>Answer:</u> The number of molecules of ethinyl estradiol present in one pill are 
<u>Explanation:</u>
To calculate the number of moles, we use the equation:
Given mass of ethinyl estradiol = 0.038 mg = 
(Conversion factor: 1 g = 1000 mg)
Molar mass of ethinyl estradiol ![(C_{20}H_{24}O_2)=[(20\times 12)+(24\times 1)+(2\times 16)]=296g/mol](https://tex.z-dn.net/?f=%28C_%7B20%7DH_%7B24%7DO_2%29%3D%5B%2820%5Ctimes%2012%29%2B%2824%5Ctimes%201%29%2B%282%5Ctimes%2016%29%5D%3D296g%2Fmol)
Putting values in above equation, we get:
According to mole concept:
1 mole of a compound contains 
number of molecules
So, 
of ethinyl estradiol will contain = 
number of molecules
Hence, the number of molecules of ethinyl estradiol present in one pill are
Answer:
33 g of H2
Explanation:
N2 + 3 H2 -> 2 NH3
3 mol H2 -> 2 mol NH3
x -> 11 mol NH3
x= (11 mol NH3 * 3 mol H2)/ 2 mol NH3
x= 16.5 mol H2
1 mol H2 -> 2 g
16.5 mol H2 ->x
x= (16.5 mol H2 * 2 g)/ 1 mol H2
x= 33 g
