Please tell the answer of the following using correct method of explanation/using formulas :-
Q1. A gold sample contains 90% gold and the rest copper. How many atoms of gold are present in one gram of this sample of gold?
Q2. A silver ornament of mass 'm' gram is polished with gold equivalent to 1% of the mass of silver. Compute the ratio of the number of atoms of gold and silver in the ornament.
Q3. A sample of ethane (C2H6 ) gas has the same mass as 1.5*10²⁰ molecules of methane (CH4). How many C2H6 molecules does the sample of gas contain?
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Answer:
Correct option is
D
2.77×10
21
As sample is 90% pure wrt to Gold,
So one gram of sample will have 90/100=0.9gm gold.
Number of moles of gold =
Atomic mass of gold
Mass of gold
=
197
0.9
=0.0046
According to mole concept,
One mole of gold contains N
A
atoms =6.022×10
23
atoms,
∴0.0046 mole of gold will contain =0.0046×6.022×10
23
=2.77×10
21