Chemistry, 17.01.2020 00:31 debiruuu

Asolid sample contains about 200ppm (w/w) of ca. how many mg of sample must be dissolved in 100ml in order to give a solution that is about 1ppm (w/v) of ca after dilution?

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Answer from: chloeboo

We need to add $5 \times 10^{-4}$ mg

Explanation:

Remember first:

$ppm(w/w) = \frac{g_{solute}}{g_{solution}}\times 10^{-6}\\ppm(w/v)= \frac{1 g_{solute}}{1000mL_{solution}}\\g_s= grams\ of\ sample\\mL_s= mL\ of\ sample$

To calculate this mass, we need to calculate the concentration as follows:

$\frac{x\ mg_s}{100mL_s} \times \frac{1g_s}{1000 mg_s} \times \frac{200gCa}{g_s} \times 10^6= 2000x \frac{gCa}{mL_s}$

Here we have the concentration of the sample in terms of x, being x the mg needed to have a solution of 1ppm (w/v). Therefore, we solve the system as follows:

$2000x \frac{gCa}{mL_s}=\frac{1gCa}{1000mL_s}\\x= \frac{1mL_s}{2000\times 1000}= 5\times 10^{-7} g= 5\times 10^{-4} mg$

Finally we need $5\times 10^{-4}$ mg of sample to have a Ca concentration of 1ppm (w/v) in the final solution.

Answer from: Quest

explanation:

the largest database of organic compounds lists about 10 million substances, which include compounds originating from living organisms and those synthesized by chemists. the number of potential organic compounds has been estimated at 1060—an astronomically high number. the existence of so many organic molecules is a consequence of the ability of carbon atoms to form up to four strong bonds to other carbon atoms, resulting in chains and rings of many different sizes, shapes, and complexities. the simplest organic compounds contain only the elements carbon and hydrogen, and are called hydrocarbons. even though they are composed of only two types of atoms, there is a wide variety of hydrocarbons because they may consist of varying lengths of chains, branched chains, and rings of carbon atoms, or combinations of these structures. in addition, hydrocarbons may differ in the types of carbon-carbon bonds present in their molecules. many hydrocarbons are found in plants, animals, and their fossils; other hydrocarbons have been prepared in the laboratory. we use hydrocarbons every day, mainly as fuels, such as natural gas, acetylene, propane, butane, and the principal components of gasoline, diesel fuel, and heating oil. the familiar plastics polyethylene, polypropylene, and polystyrene are also hydrocarbons. we can distinguish several types of hydrocarbons by differences in the bonding between carbon atoms. this leads to differences in geometries and in the hybridization of the carbon orbitals.

Answer from: Quest

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