Answer: The first question’s answer is 2 and the second question answer is 3. 12.B, 13.C
Explanation:
Answer:
0.01744 M is the hardness of the groundwater.
1,744 ppm is the hardness of the groundwater in parts per million of calcium carbonate by mass.
Explanation:

In = Indicator
Concentration of calcium ion in groud water = 
Volume of ground water = 
Concentration of EDTA solution = 
Volume of EDTA solution = 



![[CaCO_3]=[Ca^{2+}]](https://tex.z-dn.net/?f=%5BCaCO_3%5D%3D%5BCa%5E%7B2%2B%7D%5D)
So. ![[CaCO_3]=0.01744 M](https://tex.z-dn.net/?f=%5BCaCO_3%5D%3D0.01744%20M)
0.01744 M is the hardness of the groundwater.
0.01744 Moles of calcium carbonate are present in 1 Liter of solution.
Mass of 0.01744 moles of calcium carbonate =

1 g = 1000 g
1.744 g = 1.744 × 1000 mg = 1,744 mg

The hardness of the groundwater in parts per million :

1,744 ppm is the hardness of the groundwater in parts per million of calcium carbonate by mass.
The compound that has higher mass percent is Mg3N2 which is 72%
explanation
calculate the % mass of Mg in each compound
% composition of mg= molar mass of Mg/ total molar mass of the compound x100
in MgO = 24 /40 x100 = 60%
in Mg3N2 =72/100 x100 = 72 %
therefore the % composition in Mg3N2 is higher
Answer:
A. the iron atoms are gaining kinetic energy
Explanation:
when the iron melted and solidifies it loses potential energy and changes to kinetic energy