[nurikoned]

In addition to determining the elemental composition of pure unknown compounds, combustion analysis can be used to determine the purity of known compounds. A sample of 2-naphthol, C10H7OH, which is used to prepare antioxidants to incorporate into synthetic rubber, was found to be contaminated with a small amount of LiBr. The combustion analysis of this sample gave the following results: 77.48% C and 5.20% H. Assuming that the only species present are 2-naphthol and LiBr, calculate the percentage purity by mass of the sample.

[nurikoned]

Dolomite is a mixed carbonate of calcium and magnesium, calcium and magnesium carbonates both decompose to produce metal oxides (MgO and CaO). If 4.84g of residue consisting of MgO and CaO remains when 9.66g of dolomite is heated until decomposition is complete, what percentage by mass of the original sample was MgCO3?

[chenbeier]

What is your own attempt? Think to express two equation by using moles and molar mass. What is the relationship of the oxides and the carbonates?

[chenbeier]

What is your own attempt? Calculate the percentage of the 100% compound. Don´t forget the oxygen. Using molar mass.
Compare with the existing percentage.

[nurikoned]

A reaction vessel contains 5.77 g of white phosphorus and 5.77 g of oxygen. The first reaction to take place is the formation of phosphorous (III) oxide, P406; P4 (s) + 3O2 (g) --> P406(s). IF enough oxygen is present, the oxygen can react further w/ this oxide to produce phosphorus (V0 oxide, P4010; P406 (s) + 2 O2 (g) --> P4010 (s). (a) What is the limiting reactant for the formation of P4010? (b) What mass of P4010 is produced? (c) how many grams of the excess reactant remain in the reaction vessel?
Thank you

[Arkcon]

Hi there, nurikoned:, I've gone and merged your many topics together.  So everyone can see them all at once, and you can use the help you get for one, to help you solve the others, for yourself.  I'd like to take this time to remind you to read our Forum Rules{click}.  You already accepted the rules when you signed up for our forum, and you have to follow them, whether you agree with them or not, or even if you're unaware of them.  We want to see you do some work, on your own, and we'll help.  We don't dump complete answers, for anyone, not for a high school student, nor a hard-working professional, nor even the home chemist working on their newest invention.

Why not do, as much as you can, of one of them, so we can see what help you need.