20. an atom has a mass of 50 and 20 protons. how many
neutrons does it have?

30  

Explanation:

The mass number (A) is the sum of the numbers of protons and neutrons .

A = p + n

If p = 20,  

n = A - p = 50 - 20 = 30

1.solid

2.carbon dioxide

3.helium

consider the reaction below.

 no rx

at 500 k, the reaction is at equilibrium with the following concentrations.

[pci5]= 0.0095 m

[pci3] = 0.020

[ci2] = 0.020 m

what is the equilibrium constant for the given reaction?

0.042

0.42

2.4

24