Q36 of 37 Page 22

Chlorine is prepared in the laboratory by treating manganese dioxide (MnO2) with aqueous hydrochloric acid according to the reaction


How many grams of HCl react with 5.0 g of manganese dioxide?

Given:

Mass of Manganese Dioxide = 5 g


Atomic Mass of Manganese = 55g


Atomic Mass of Oxygen = 16g


Atomic Mass of Hydrogen = 1g


Molecular Mass of MnO2 = 55 + [16×2]


= 55 + 32


= 87g


Molecular Mass of HCl = 1 + 35.5


= 36.5g


So by observing the chemical reaction we see that,


1moles of MnO2 reacts with 4moles of HCl


87g of MnO2→ 4×36.5g of HCl


So 5g of MnO2→ X g of HCl


X = [146×5]/87


X = 730/87


X = 8.39g


So, 8.4g of HCl will react completely with 5g of MnO2.


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Calculate the number of atoms in each of the following:

(i) 52 moles of Ar


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A welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives 3.38 g carbon dioxide, 0.690 g of water and no other products. A volume of 10.0 L (measured at STP) of this welding gas is found to weigh 11.6 g. Calculate

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What mass of CaCO3 is required to react completely with 25 mL of 0.75 M HCl?