Answer:
These are the chemical names and molecular formula of the compounds formed from these elements:
- Rubidium + Bromine = <em>Rubidium bromide, RbBr</em>
- Strontium + Sulphur = <em>Strontium sulfide, SrS</em>
- Barium and Chlorine = <em>Barium chloride, </em>
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Thallium is the element that has 81 protons in the nuclei of its atoms. I hope I answered it to the extent you needed.
Answer:
0.249087
Explanation:
1.5 x 10^23 atoms x 1 mole / 6. 022 x 10^23 atoms
= 0.249087
Isotopes are atoms of the same element that have different masses. The relative atomic mass (am) is a weighted average that takes into account the abundance of each isotope. We can calculate the relative atomic mass using the following expression.

where,
- abi: percent abundance of each isotope
For Gallium,
[1]
where "x" and "y" are the unknown abundances.
We also know that the sum of both abundances must be 100%.
x + y = 100
y = 100 - x [2]
If we replace [2] in [1], we get

Then, in [2]
y = 100 - x = 100 - 20.5 = 79.5
In conclusion, Ga-69 has an abundance of 20.5% and Ga-71 has an abundance of 79.5%.
You can learn more about isotopes in: brainly.com/question/21536220?referrer=searchResults
Answer:

Explanation:
Mass of stock solution = 20 g
Molar mass of NaOH = 40 g/mol
Volume of stock solution = 0.150 mL
= Concentration of NaOH for the final solution
= Amount of stock solution taken = 15 mL
= Total volume of solution = 65 mL
Molarity is given by

We have the relation

The concentration of NaOH for the final solution is
.