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The complete question probably is
The pH scale for acidity is defined by pH = − log₁₀[H⁺] where [H⁺] is the concentration of hydrogen ions measured in moles per liter (M). A solution has a pH of 2.55. Find the hydrogen ion concentration.
Answer: -
0.003 M
Explanation: -
pH = − log₁₀[H⁺]
Thus the hydrogen ion concentration [H⁺] = 
= 
= 0.003 M
Given an equilibrium constant value of 7.2 x 10-4 it is false to say that the reaction proceeds essentially to completion.
<h3>What is the equilibrium constant?</h3>
In a reaction, we can judge using the value of the equilibrium constant weather or not the reaction moves on to completion. If the reaction moves up to completion, it the follows that the value of the equilibrium constant ought to be large.
On the other hand, when we have a case that the equilibrium constant is small and is not so large, then the reaction does not proceed essentially to completion.
Given an equilibrium constant value of 7.2 x 10-4 it is false to say that the reaction proceeds essentially to completion.
Learn more about equilibrium constant:brainly.com/question/10038290
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3.5 M has 3.5 moles per litre
so we have one litre, so we need 3.5 moles
moles = mass/molarmass
3.5 * 23 = 80.5
A pH scale runs from 1 to 14 with 7 being neutral.
1-6 has base like properties
8-14 has avid line properties
since this solution has a pH scale of 4.... the solution is basic
Answer : The expression for solubility constant for this reaction will be,
![K_{sp}=[Ca^{2+}]^3[PO_4^{3-}]^2](https://tex.z-dn.net/?f=K_%7Bsp%7D%3D%5BCa%5E%7B2%2B%7D%5D%5E3%5BPO_4%5E%7B3-%7D%5D%5E2)
Explanation :
Solubility product : It is defined as the product of the concentration of the ions that present in a solution raised to the power by its stoichiometric coefficient in a solution of a salt. This takes place at equilibrium only.
The solubility product constant is represented as,
.
The dissociation of calcium phosphate is written as:

The expression for solubility constant for this reaction will be,
![K_{sp}=[Ca^{2+}]^3[PO_4^{3-}]^2](https://tex.z-dn.net/?f=K_%7Bsp%7D%3D%5BCa%5E%7B2%2B%7D%5D%5E3%5BPO_4%5E%7B3-%7D%5D%5E2)