Answer:
a
Explanation:
it is A because h20 and c02 are molecules while what make them up are atoms
Answer:
B. 
Explanation:
The unit for rate is M/s while the unit for each molecule should be M. You can find the unit for k by putting the units for rate and the molecules into the equation
rate= k{X][Y]
M/s= k *
* 
k= (M/s) / (
)
k= 
You can also use this predetermined formula to solve this problem faster: k= 
Where n is the number of molecule. There are 3 molecule(2X and 1Y) so n=3, so
k= 
k=
=
= 
Yes, you should memorize them. While it is easy to predict them by looking at a periodic table, you should still have a strong grasp of simpler chemistry such as this before more challenging topics are taught.
I believe it forms an anion that has a larger radius.
A is correct. water is incompressible, so it will always have the same density, regardless of volume