we have a total of three times the original number (6.923 * 10**-7) moles of all ions, or 2.077 * 10**-6 moles of ions
<h3>What is aragonite-strontianite solid solution dissolution in nonstoichiometric Sr (HCO3)2 solutions?</h3>
Synthetic strontianite-aragonite solid-solution minerals were dissolved in non-stoichiometric CO2-saturated Sr(HCO3)2 and Ca(HCO3)2 solutions at 25°C. The reactions in Sr(HCO3)2 solutions frequently become incongruent, precipitating a Sr-rich phase before attaining stoichiometric saturation. Mechanical mixes of solids approach stoichiometric saturation in terms of the least stable solid in the combination.
This surficial phase has a thickness of 0-10 atomic layers in Sr(HCO3)2 solutions and a thickness of 0-4 layers in Ca(HCO3)2 solutions and dissolves and/or recrystallizes within 6 minutes of reaction.
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Answer:
Total mass of the reactant = 2+2.5 =4.5 mg
Total mass of product = 4.15 mg
therefore, mass of unreacted oxygen = 4.50-4.15 = 0.35 g
<h2>
Hello!</h2>
The answer is:
The empirical formula is the option B. 
<h2>
Why?</h2>
The empirical formula of a compound is the simplest formula that can be written. On the opposite, the molecular formula involves a variant of the same compound, but it can be also simplified to an empirical formula.

We are looking for a formula that cannot be simplified by dividing the number of molecules/atoms that conforms the compound.
Let's discard option by option in order to find which formula is an empirical formula (cannot be simplified)
A. 
It's not an empirical formula, it's a molecular formula since it can be obtained by multiplying the empirical formula of the same compound.

B. 
It's an empirical formula since it cannot be obtained by the multiplication of a whole number and the simplest formula. It's the simplest formula that we can find of the compound.
C. 
It's not an empirical formula, it's a molecular formula since it can be obtained by multiplying the empirical formula of the same compound.

D. 
It's not an empirical formula, it's a molecular formula since it can be obtained by multiplying the empirical formula of the same compound.

Hence, the empirical formula is the option B. 
Have a nice day!
Answer:
kilogram is used to measure to mass