Explanation:
Standard formation of an substance is defined as formation of one mole of substance from its constituting elements.
Chromium(III) nitrate is composed of chromium, nitrogen and three oxygen atoms.

A balanced chemical equation for the standard formation reaction of solid chromium(III) nitrate

Aqueous Solution - The expected precipitate would consist of Cu(OH)2.
What is aqueous solution?
An aqueous solution is one in which water serves as the solvent. Chemical equations typically illustrate it by adding (aq) to the appropriate chemical formula. For instance, Na+(aq) + Cl would be used to represent a solution of table salt, as well as sodium chloride (NaCl), throughout water (aq). The word aqueous, which derives from the word aqua, means that it is dissolved in or related to water. Water is a common solvent in chemistry due to its superior solvent properties and natural abundance. Since water is frequently used as a solvent in experiments, unless the solvent is specified, the word "solution" refers to an aqueous solution. A solution wherein the solvent is a liquid but not water is referred to as a non-aqueous solution.
Because:
salt: copper(II) hydroxide
Ksp: 1.8 × 10-19
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Answer: The empirical formula is 
Explanation:
If percentage are given then we are taking total mass is 100 grams.
So, the mass of each element is equal to the percentage given:
Mass of Na= 34.5 g
Mass of B= 16.4 g
Mass of O = 48.6 g
Step 1 : convert given masses into moles.
Moles of Na =
Moles of B =
Moles of O =
Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.
For Na = 
For B = 
For O =
The ratio of Na: B: O= 1: 1: 2
Hence the empirical formula is 