Which of the following substances is a weak base?
a. naoh
b. nh3
c. k2o
d. koh

b. NH₃.

Explanation:

Base is the substance that can produce OH⁻ ions in the solution.

So, NaOH, KOH, and NH₃ are bases because they can produce OH⁻ ions in the solution.

But, K₂O is not a base, it can not produce OH⁻ ions in the solution.

Strong bases are bases that can completely ionized in the solution and produce OH⁻ ions.

NaOH and KOH are strong bases because they can completely ionized in the solution and produce OH⁻ ions.

Weak bases are bases that can not completely ionized (ionized partially) in the solution and produce OH⁻ ions.

NH₃is a weak base hat can not completely ionized (ionized partially) in the solution and produce OH⁻ ions.

So, the right choice is: NH₃.

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"