Where did the periodic table come from

2 answers:

8 0

In 1869 a Russian chemist called Dmitry Mendeleev published a regular table just five years after John Newlands introduced his Law of Octaves. Mendeleev also arranged in the order of relative atomic mass elements known at that time, but he did some other things, making his table much better.

777dan777 [17]3 years ago

8 0

In 1869, just five years after John Newlands put forward his Law of Octaves, a Russian chemist called Dmitri Mendeleev published a periodic table. Mendeleev also arranged the elements known at the time in order of relative atomic mass, but he did some other things that made his table much more successful.

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Combustion analysis of 1.200 g of an unknown compound containing carbon, hydrogen, and oxygen produced 2.086 g of CO2 and 1.134

timurjin [86]

the empirical formula is C3H8O2 You need to determine the relative number of moles of hydrogen and carbon. So you first calculate the molar mass of CO2 and H20 Atomic weight of carbon = 12.0107 Atomic weight of hydrogen = 1.00794 Atomic weight of oxygen = 15.999 Molar mass CO2 = 12.0107 + 2 * 15.999 = 44.0087 Molar mass H2O = 2 * 1.00794 + 15.999 = 18.01488 Now calculate the number of moles of CO2 and H2O you have Moles CO2 = 2.086 g / 44.0087 g/mole = 0.0474 mole Moles H2O = 1.134 g / 18.01488 g/mole = 0.062948 mole Calculate the number of moles of carbon and hydrogen you have. Since there's 1 carbon atom per CO2 molecule, the number of moles of carbon is the same as the number of moles of CO2. But since there's 2 hydrogen atoms per molecule of H2O, The number of moles of hydrogen is double the number of moles of H2O Moles Carbon = 0.0474 Moles Hydrogen = 0.062948 * 2 = 0.125896 Now we need to determine how much oxygen is in the compound. Just take the mass of the compound and subtract the mass of carbon and hydrogen. What's left will be the mass of oxygen. Then divide that mass by the atomic weight of oxygen to get the number of moles of oxygen we have. 1.200 - 0.0474 * 12.0107 - 0.125896 * 1.00794 = 0.503797 Moles oxygen = 0.503797 / 15.999 = 0.031489 So now we have a ratio of carbon:hydrogen:oxygen of 0.0474 : 0.125896 : 0.031489 We need to find a ratio of small integers that's close to that ratio. Start by dividing everything by 0.031489 (selected because it's the smallest value) getting 1.505288 : 3.998095 : 1 The 1 for oxygen and the 3.998095 for hydrogen look close enough. But the 1.505288 for carbon doesn't work. But it looks like if we double all the numbers, we'll get something close to an integer for everything. So do so. 3.010575 : 7.996189 : 2 Now this looks good. Rounding everything to an integer gives us 3 : 8 : 2 So the empirical formula is C3H8O2

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3 years ago

How many theoretical plates produce a chromatography peak eluting at 12.83 min with a width at half-height of 8.7 s

GrogVix [38]

Answer-Figure P38.63a
is a three-dimensional sketch of a birefringent crystal. The dotted lines illustrate how a thin, parallefaced slab of material could be cut from the larger specimen with the crystal’s optic axis parallel to the faces of the plate.”

Sorry if it’s it correct

4 0

3 years ago

What is the molecular formula of a molecule that has an empirical formula of CH and a molecular mass of 78.11 g

sveticcg [70]

Answer: C6H6

Explanation: Molecular Formula is the molecular mass divided by the empirical formula mass of CH which is C 12and H is 1 so 12 + 1= 13 g CH

Solution:

78.11 g CH / 13 g CH = 6

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Gelneren [198K]