Question

A. In the experiment, The molar volume of a gas. Mg (s) + 2HCl (aq) = MgCl₂​ (aq) + H₂ ​(g), the magnesium ribbon was dissolved in hydrochloric acid, a monoprotic acid, to produce H₂ ​gas. If phosphoric acic, a triprotic acid, were used to react with the magnesium rather than hydrochloric acid, does that affect the amount of H₂​ gas produced?. Write balanced equations for the reaction og Mg with 1) HCl and 2) phosphoric acid to help explain your answer.

B. In this experiment, Mg (s) + 2HCl (aq) = MgCl₂​ (aq) + H₂ ​(g), ​you injected 5 ml of HCl into the flask and immediately pulled back the plunger to its original position. Explain (a) why this latter action was done and (b) if the plunger weren't pulled back to its original position, how would this affect the subsequent molar volume calculation (say, under STP condictions). Answer this question by stating the molar volume calculation would be higher, lower, or not affected, and proide a plausible explanation for your choice.

Answer 1

Following is the Solution of and Answer to the first question (i.e. Question - A ) of the given Question Set.....

Solution:

• Step - 1:

Balanced Equation or the Reaction of Mg ...with ... HCl is the following:

   Mg + 2 HCl = MgCl₂ + H₂ ....................... (Equation - 1)

The above balanced Chemical Equation gives .... i.e. according to Equation - 1 .....

Molar ratio: Mg : H₂ = 1 : 1 ......... (Case -1 )

• Step - 2:

  

Balanced Equation or the Reaction of Mg ...with ... Phosphoric Acid (H₃PO₄) is the following:

3Mg + 2 H₃PO₄ = Mg₃(PO₄)₂ + 3H₂ ....................... (Equation - 2)

The above balanced Chemical Equation gives .... i.e. according to Equation - 2 .....

Molar ratio: (....Case - 2 )

Mg : H₂ = 3 : 3 = 1:1 ..... same ratio to the ratio we have obtained above for the reaction between Mg and HCl .....i.e.. Equation - 2.......

Step-3:

Therefore...... the Answer would be the following...

• Answer:

Since we can see that in both of the above Cases the molar ratio of Mg:H₂ ...remains the same.constant,, i.e. molar ratio = 1 : 1 remains constant in both of the above cases (i.e....reaction(s) with . HCl and H₃PO₄ ).

Therefore, If we react a certain amount (i.e. moles) of Mg with H₃PO₄instead of reacting the same amount of Mg with HCl​, in both cases, there wouldn't be any change in the amount /moles of produced H₂.....and amount of H₂ produced will not be affected and will remain the same, in both cases....

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