What do you mean by this?
Explanation:
Bring to the boil. Carefully place the can in the saucepan, ensuring there's enough water to completely cover the can at all times, topping up water frequently throughout the cooking process. Simmer, uncovered for 3 hours. Ensure the can is completely covered with water at all times during cooking
A three dimensional circular shape would be a sphere :)
Answer:
The energy of attraction between the cation and anion is 1.231 X 10⁻¹¹ J
Explanation:
Let the charge on the cation be q₁
Also let the charge on the anion be q₂
A cation q₁ with a valence of 1, has a charge of 1 X 1.602×10⁻¹⁹C = 1.602×10⁻¹⁹C
An anion q₂ with a valence of 3, has a charge of 3 X 1.602×10⁻¹⁹C = 4.806 ×10⁻¹⁹C
The distance between the two charges is 7.5nm = 7.5 X10⁻⁹m
Energy of attraction = 
Where k is coulomb's constant = 8.99 X 10⁹ Nm₂/C₂
Energy of attraction = 
Energy of attraction = 1.231 X 10⁻¹¹ J
Therefore, the energy of attraction between the cation and anion is 1.231 X 10⁻¹¹ J