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Colt1911
2 months ago
5

An impure sample of zinc (zn) is treated with an excess of sulfuric acid (h 2 so 4) to form zinc sulfate (znso4) and molecular h

ydrogen (h 2). (a) write a balanced equation for the reaction. (b) if 0.0764 g of h 2 is obtained from 3.86 g of the sample, calculate the percent purity of the sample. (c) what assumptions must you make in (b)
Chemistry
1 answer:
VMariaS [2.9K]2 months ago
7 0

a) The completely balanced chemical reaction is:

 

Zn(s) + H2SO4(aq) --------> ZnSO4(aq) + H2 (g) 

<span>b) Initially, we determine the quantity of zinc that has reacted based on the produced H2.</span>

According to stoichiometry, 1 mole of Zn is required for each mole of H2 created, thus:

moles(Zn) = moles(H2) 

where moles are calculated as the ratio of mass to molar mass (MM)
mass(Zn) / MM(Zn) = mass(H2) / MM(H2) 
mass(Zn) = [mass(H2) / MM(H2)] * MM(Zn) 
mass(Zn) = [(0.0764 g)/(2 g/mol)] * 65.38 g/mol 
mass(Zn) = 2.49 g 

Consequently, we find 2.49 g of pure zinc in the sample, leading to a purity of zinc of: 

purity = (2.49 / 3.86) * 100 % = 64.50 % 
 

<span>c) In part (b), it is assumed that the impurities in the sample do not react with sulfuric acid to emit hydrogen. Thus, the hydrogen solely arises from the reaction of Zn with sulfuric acid.</span>

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