If an undetected bubble of air were trapped inside the gas collection tube, woul

Question

If an undetected bubble of air were trapped inside the gas collection tube, would your value of R be erroneously high, erroneously low, or be unaffected by the bubble of air? Explain. The amount of hydrochloric acid added to the reaction was more than enough to consume all of the magnesium. Therefore, the magnesium is the limiting reactant. How many milliliters of 12 M hydrochloric acid solution is necessary to consume 0.080 grams of magnesium metal? If you hadn't added quite enough hydrochloric acid to consume all of the magnesium metal, would your value of R be erroneously high, erroneously low, or be unaffected? Explain.

Explanation / Answer

1) presence of air bubble results in the decrease in the actual volume of gas, we know R is proportional to Volume , actually we should get low values of R .So here we get more value of R .This is erroneously high

2)

Grams of magnesium metal = 0.080 g

Moles of magnesium = 0.080 g / 24.3 = 0.0033 moles

1 mole of Mg reacts with 2 moles of HCl

So moles of HCl need = 2*0.0033 moles = 0.0066 moles

Volume of HCl = 0.0066 moles / 12 M = 0.00055 L = 0.55 mL

3) if enough amount of HCl is not added , then we lose of Mg in the reactants .So in calculating R,

R = PV*M/m*T

Here we are taking total mass , but actually less mass is reacted. So the R we get is greater than the actual R value .

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