Answer:
There is 18.8% lithium by mass in second sample
Explanation:
Both the two samples are pure lithium carbonate. So % lithium by mass will be same in both samples. This can be proved mathematically as follows-
Let's assume weight of first sample is x g
So, 100 g of sample contains 18.8 g of lithium
Hence, x g of sample contains 
g of lithium
Now, the second sample has weight equal to 2x g
So, 2x g of sample contains 
g of lithium
So, % lithium by mass in second sample = 
% = 18.8%
Answer:
H2
Explanation:
H (or hydrogen), being a halogen, as an atom, has 7 valence electrons. This means that it naturally bonds with another atom of the same isotope in order to reach the desired total of valence electrons: 8.
So... H+H = H2. EZ
The balanced chemical reaction would be:
2H2 + O2 = 2H2O
We are given the amount of oxygen to react with hydrogen. To determine the amount of hydrogen needed for the oxygen to completely react, we use the balanced reaction to relate the substances. We do as follows:
64 g O2 ( 1 mol / 32 g ) ( 2 mol H2 / 1 mol O2 ) ( 2.02 g / 1 mol ) = 8.08 g of hydrogen gas needed
