Question

Bell metal contains 80% copper. The mass of Bell metal which contains 1.5x10- atoms of copper
1)2mg
2)20mg
3)40mg
4)12.8mg​

Answer 1

Answer:

40mg

Explanation:

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Answer 2

Answer:

According to Avogadro's constant, 1 mole of a any substance has exactly 6.022 × 10²³ atoms or molecules.

Find the number of moles in the bell metal:

If 6.022 × 10²³ atoms = 1 mole

Then 1.5 × 10^20 = 1 ×1.5 x 10^20/6.022 × 10²³

= 0.00025 moles

molar mass of Cu is 64

mass = moles × molar mass

= 0.00025 mol × 64g/mol

= 0.016 g

Therefore 1.5×10^20 atoms of copper has a mass of 0.016 g

This 80% of the piece of metal, weight of the mass is 100%

= 100/80 × 0.016

= 0.02 g

The piece of metal has a mass of 0.02 g

Ans:2mg