How many moles make up 350g of table salt, NaCl in .NET

Encoder EAN-13 Supplement 5 in .NET How many moles make up 350g of table salt, NaCl

The average volume of a human breath is roughly 500 mL How many moles do you inhale with each breath on a day when the temperature hovers near freezing Assuming that human exhalations eventually intermix evenly throughout the approximately 3 1022L of Earth s atmosphere, calculate how many molecules from Genghis Khan s last breath you take into your lungs each time you inhale

If you fill a 2L soda bottle (at STP) with carbon dioxide, how many particles does the bottle contain

Chemists often are concerned with precisely what percentage of a compound s mass consists of one particular element Lying awake at night, uttering prayers to Avogadro, they fret over this quantity, called percent composition Calculating percent composition is trickier than you may think Consider the following problem, for example The human body is composed of 60 to 70 percent water, and water contains twice as many hydrogen atoms as oxygen atoms If two-thirds of every water molecule is hydrogen and water makes up 60 percent of the body, it seems logical to conclude that hydrogen makes up 40 percent of the body Yet hydrogen is only the third most abundant element in the body by mass What gives Oxygen is 16 times more massive than hydrogen So, equating atoms of hydrogen and atoms of oxygen is a bit like equating a toddler to a sumo wrestler When the doors of the elevator won t close, the sumo wrestler is the first one you should kick out, weep though he may Within a compound, it s important to sort out the atomic toddlers from the atomic sumo wrestlers To do so, follow three simple steps

explain in the previous section Percent compositions are completely irrelevant to gram atomic masses, because these apply only to pure monatomic substances; by definition, these substance have 100 percent composition of a given element

Multiply each fractional quotient by 100% Voil ! You have the percent composition by mass of each element in the compound

Calculate the percent composition for each element present in sodium sulfate, Na2SO4 Na: 324%, S: 225%, O: 451% The gram formula mass of sodium sulfate is (2 230g mol 1) + (1 320g mol 1) + (4 160g mol 1) = 142g mol 1 Of each mole of compound, 2 230g = 460g are sodium 1 320g = 320g are sulfur 4 160g = 640g are oxygen Dividing each of these quantities by the molar mass of sodium sulfate (142g) yields the percent composition: 46g 32g 64g 100 = 324% sodium, 100 = 225% sulfur, and 100 = 451% oxygen 142g 142g 142g As a check, add the three percentages to ensure they equal 100%: 324% + 225% + 451% = 100%

What if you don t know the formula of a compound Chemists sometimes find themselves in this disconcerting scenario Rather than curse Avogadro (or perhaps after doing so), they analyze samples of the frustrating unknown to identify the percent composition From there, they calculate the ratios of different types of atoms in the compound They express these ratios as an empirical formula, the lowest whole number ratio of elements in a compound To find an empirical formula given percent composition, use the following procedure:

The beauty of this little trick is that you conveniently gift yourself with the same number of grams of each elemental component as its contribution to the percent composition For example, if you assume that you have 100g of a compound composed of 603% magnesium and 397% oxygen, you know that you have 603g of magnesium and 397g of oxygen

2 Convert the assumed masses from Step 1 into moles by using gram atomic masses 3 Divide each of the element-by-element mole quantities from Step 2 by the lowest