Question

1.5 x 10^20 molecules of a substance weigh 20mg. What is the molar mass of the substance?

Answer 1

1.5*10^20 molecules weigh =20 mg= 20 *10^(-3) g

6.022× 10^23 molecules weigh =(20*10^(−3)/1.5×10^20)*
6.022×10^23 = 80.2 g
Hence , the molecular mass of the substance is 80.2 g.

Answer 2

Answer:

80g

Explanation:

N=1.5*10^20 molecules

NA=6.023*10^23

N=Given molecules/NA=1.5*10^20/

                                         6.023*10^23 {1.5 AND 6.023 WILL CANCEL}

2.49MOLES is 20mg

1 MOLE is x                    (CROSS MULTIPLICATION)

x=20/2.49=8.03=80g

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