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A sample of pure lithium carbonate contains 18.8% lithium by mass. what is the % lithium by mass in a sample of pure lithium carbonate that has twice the mass of the first sample?

a.9.40 %
b.18.8 %
c.37.6 %
d.75.2 %

User Jaredsk
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2 Answers

3 votes
18.8%.
The component percentage of a pure compound does not vary with the mass of the sample.
User Sherif Eldeeb
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4 votes

Answer:

The correct answer is option (a).

Step-by-step explanation:

The molecular formula of lithium carbonate is
Li_2CO_3

Percentage of lithium in lithium carbonate = 18.8 %

Molar mass of the lithium carbonate = M

Atomic mass of lithium = 7 g/mol


18.8\%=(2* 7 g/mol)/(M)* 100

M = 74.46 g\mol

Mass of pure lithium carbonate is twice the mass of first sample:
2* 74.46 g/mol =148.92 g/mol

Percentage of lithium in pure lithium carbonate sample:


\%=(2* 7 g/mol)/(148.92 g/mol)* 100=9.40\%

The correct answer is option (a).

User NemoXP
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