Question

From 490 mg of H2SO4 10^20 molecules are removed. The number of molecules left over are

Answer 1

Answer:

Molar mass H

2

SO

4

= 98 g/mol.

98 mg H

2

SO

4

=

1000mg/g×98g/mol

98mg

=0.001 moles.

3.01×10

20

molecules of H

2

SO

4

=

6.02×10

23

3.01×10

20

=0.0005 moles.

Number of moles of H

2

SO

4

remaining =0.001−0.0005=0.0005=0.5×10

−3

Answer 2

Answer:

(4)The number of molecules left over are

$2.91 \times 10 {}^{21}$

Explanation:

Given that,

Chemical Compund is Sulphuric Acid(H2SO4)

Mass of the given compound=490mg

No.of molecules removed from compound is

$= 10 {}^{20}$

We know that Molar mass of sulphuric acid is 98gm

Hence,no.of moles of Sulphuric acid is

$n = \frac{m}{M} = \frac{490mg}{98g} = \frac{0.49}{98} \\ = 0.005 \: mol$

Hence number of molecules in the acid can be found by multiplying moles with avadagro number

$N = 0.005 \times 6.023 \times 10 {}^{23} \\ = 3.0115 \times 10 {}^{21}$

Out of these molecules,no.of molecules removed are

$10 {}^{20}$

Hence,remaining molecules are

$3.0115 \times 10 {}^{21} - 10 {}^{20} \\ = 10 {}^{20} (30.115 - 1) \\ = 29.115 \times 1 0{}^{20} \\ = 2.91 \times 10 {}^{21}$

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