CIE Chemistry ATP P.42 MCQ query :

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Haris Sal11 said:
That's not the complete question. You're missing the names of the acid, which is necessary because of the comparison with mole ratio. I need to know which acid was used in part b. I'd know the answer then.
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Ans was c, n as far as i remember, HCl was used in a n c, while H2SO4 was used in b n d
 
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Dont quite remember bout the options, but yea only option c gave exactly double vol of hydrogen
 
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I agree the answer was A. student used different acid solution which was hydrochloric acid. and in the question 0.002 moles were prodeuced. and in A 0.004 moles were produced :)
 
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Snowysangel said:
The question stated that magnesium reacts with 10 cm3 of 0.01 moles of hcl to produce h2. Which of the following would produce double the volume of hydrogen. 1)10 cm3 of 0.02 moles/dm3 of hcl 2)20 cm3 of 0.01 moles/dm3 3)20 cm3 of 0.02 moles/dm3 4)40 cm3 of 0.01 moles/dm3
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mmm, i dun think thats the comp correct ques :confused:
 
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Ok now, ans was C. How? this is how. In the first eq, H2SO4+Mg=MgSO4+H2. Mole ratio between acid and hydrogen gas here is 1:1. So when 0.02 mol of acid was used, o.o2 mol of hydrogen gas was produced. Now the options included HCl as wel, n u had to form the 2nd eq urself. HCl was only given in A n C. New eq was 2HCl+Mg=MgCl2+H2, so mol ratio here between acid and gas is 2:1. In option C, mols of acid came to be 0.08, hence mols of hydrogen were half of this i.e 0.04, which was actually double than the hydrogen produced in the first eq
 
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