Answer:
1g Hydrogen
Explanation:
<h3><u>Getting</u><u> </u><u>to</u><u> </u><u>the</u><u> </u><u>equation</u><u>:</u></h3>Calcium in water reacts vigorously to give a cloudy white <em>Precipitate</em><em> </em>(compound) called Calcium hydroxide alongwith the evolution of Hydrogen gas.
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<h3><u>Balancing</u><u> </u><u>the</u><u> </u><u>equation</u><u>:</u><u> </u></h3>This reaction is not in it's balanced form! The number of atoms of Hydrogen on the left is 2 while that on the right is 4,I.e.,they're not equal.
Adding a 2 in front of H2O solves the problem by making the number of atoms of each element on both the sides equal.
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<h3><u>Observations</u><u>:</u></h3>Looking into the equation more carefully, we see:
<u><em>1</em><em> </em></u><em>atom</em><em> </em><em>of</em><em> </em><em>Calcium</em><em> </em><em>reacts</em><em> </em><em>with</em><em> </em><em><u>2</u></em><em> </em><em>molecules</em><em> </em><em>of</em><em> </em><em>water</em><em> </em><em>to</em><em> </em><em>give</em><em> </em><u><em>1</em><em> </em></u><em>molecule</em><em> </em><em>of</em><em> </em><em>Calcium</em><em> </em><em>Hydroxide</em><em> </em><em>alongwith</em><em> </em><em><u>1</u></em><em> </em><em>molecule</em><em> </em><em>of</em><em> </em><em>Hydrogen</em><em> </em><em>gas</em><em>.</em>
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<h3><u>Gram</u><u> </u><u>atomic</u><u> </u><u>and</u><u> </u><u>molecular</u><u> </u><u>masses</u><u> </u></h3><u>Mass</u><u> </u><u>of</u><u> </u><u>one</u><u> </u><u>atom</u><u> </u><u>of</u><u> </u><u>Calcium</u><u> </u>= it's gram atomic mass
= 40 g
<u>Mass of one "molecule" of Hydrogen</u>
= it's Gram molecular mass
= gram mass of one atom × number of atoms in one molecule
= 1 × 2
= 2 g
So,
according to our observation:
One atoms of Calcium gives one molecule of Hydrogen <em>(during the particular reaction)</em>
=><u> 40g of Calcium gives = 2g of Hydrogen</u>
•°• 1 g of Calcium gives =
= g Hydrogen
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<h3><u>Answer</u><u>:</u></h3>We're provided with 20g of Calcium,
=> 20g of Calcium gives = 20 × g H2
<u>= 1 g H2</u>
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Hope this helps!