Question

When 0.1 g of magnesium is treated with an
excess of hydrochloric acid, what volume of
gas at room temperature and pressure will be
produced?
(a) 10 cm
(b) 25 cm3
(C) 48 cm
(d) 100 cm3
​

Answer 1

Answer:

I believe its b.

Explanation:

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Answer 2

Answer:

This is an ideal gas law problem, at least at the heart of the question. The ideal gas law is:

PV = nRT

Where P is the pressure in atm, V is the volume in L, n is the number of moles, R is the gas constant (0.082 atm-L/mol-K) and T is the temperature in K. Under room temperature/typical atmospheric pressure, T will be about 20º C or 293 K and the pressure will be about 1 atm.

Now, all we need is to determine ‘n’.

When Mg is mixed with hydrochloric acid (HCl) hydrogen (H2) is produced:

Mg(s) + 2 HCl (aq) → MgCl2(aq) + H2(g)

and for every mole of gas (H2) produce, one mole of Mg is consumed. The molecular weight of Mg is 24.3 g/mole so 0.1 g corresponds to 0.00417 moles and will result in the formation of the same number of moles of H2.

Rearranging the gas law to solve for V and then putting the numbers in gives

V =nRT/P = (0.00417 moles) * (0.082 atm-L/mol-K) * (293 K)/(1 L) = 0.1 L or 100 mL or 10dm3