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Mrac [35]
2 years ago
7

When Dimitri Mendelev first developed the periodic table, one of the most important features that he introduced was starting a n

ew row at a certain point. What factor was most important to Mendelev in knowing when to end a row (period) and start a new one
Chemistry
2 answers:
yuradex [85]2 years ago
3 0

Mendleev arranged the elements based on atomic mass and the properties.

He ended a row and started a new row based on chemical properties.

He observed a drastic change in chemical properties of elements so he started new row.


omeli [17]2 years ago
3 0

Answer:

When elements started to show drastically different properties he knew to end the period and start a new row.

Explanation:

Mendelev arranged elements according to their atomic mass and not atomic number. Mendeleev discovered that the physical and chemical properties of element vary periodically and that is how he arranged the elements in the periodic table. He left gaps for undiscovered elements and those elements that were indeed discovered later where found to have properties close to Mendelev’s prediction.

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Molten gallium reacts with arsenic to form the semiconductor, gallium arsenide, GaAs, used in light-emitting diodes and solar ce
Vsevolod [243]

Answer:

a) 1.2g of arsenic b) 0.64g of arsenic c) 3.481g of gallium d) 3.806g of gallium e) 2.61g arsenic

Explanation:

The balanced equation is:

Ga + As = GaAs, 1:1 mole ratio

a) mass (gallium)/ molar mass of Ga = 4/ 69.723 = 0.0574mol

Mass (arsenic)/ molar mass of As = 5.5/74.9216 = 0.0734, subtracting the moles from each other (knowing already that the ratio is 1:1), arsenic is in excess by 1.2g

b) repeating the procedure (changing the values)

It will be 0.0574 to 0.06593

Arsenic is in excess by 0.00854

0.00854* mass of arsenic (such must be done for the first remaining mole) = 0.64g

c) the mole ratio is 0.0574: 0.00747

Gallium is in excess by 0.05

Mass of excess gallium = 0.05* 69.723 = 3.481g

d) using the mass given, the new ratio is

0.128: 0.0734

Gallium is in excess by 0.054mol

Mass of excess gallium = 0.054*69.723 = 3.806g

e) using the mass again, the new ratio is 0.0574: 0.02,

Gallium is in excess by 0.0374*69.723 = 2.61g

7 0
3 years ago
Please help with #2 and #3
Vaselesa [24]

Answer:

2. V_2=17L

3. V=82.9L

Explanation:

Hello there!

2. In this case, we can evidence the problem by which volume and temperature are involved, so the Charles' law is applied to:

\frac{V_2}{T_2}=\frac{V_1}{T_1}

Thus, considering the temperatures in kelvins and solving for the final volume, V2, we obtain:

V_2=\frac{V_1T_2}{T_1}

Therefore, we plug in the given data to obtain:

V_2=\frac{18.2L(22+273)K}{(45+273)K} \\\\V_2=17L

3. In this case, it is possible to realize that the 3.7 moles of neon gas are at 273 K and 1 atm according to the STP conditions; in such a way, considering the ideal gas law (PV=nRT), we can solve for the volume as shown below:

V=\frac{nRT}{P}

Therefore, we plug in the data to obtain:

V=\frac{3.7mol*0.08206\frac{atm*L}{mol*K}*273.15K}{1atm}\\\\V=82.9L

Best regards!

6 0
3 years ago
Two samples of the same compound are compared. what does the data represent? sample 1: 24.22 g carbon and 32.00 g oxygen sample
goblinko [34]

According to law of definite proportion:

In a compound, elements are always arranged in fixed ratio by mass.

Here, sample 1 has 23.22 g Carbon and 32.00 g Oxygen.

Converting mass into number of moles:

Molar mass of carbon is 12 g/mol and that of oxygen is 16 g/mol thus,

n_{C}=\frac{m_{C}}{M_{C}}=\frac{24.22 g}{12 g/mol}\approx 2 mol

Similarly, number of moles of oxygen will be:

n_{O}=\frac{m_{O}}{M_{O}}=\frac{32 g}{16 g/mol}=2 mol

The ratio of number of moles of carbon and oxygen will be:

C:O=n_{C}:n_{O}=2:2=1:1

Therefore, formula of compound will be CO.

Sample 2:

It has 36.22 g Carbon and 48.00 g Oxygen.

Converting mass into number of moles:

Molar mass of carbon is 12 g/mol and that of oxygen is 16 g/mol thus,

n_{C}=\frac{m_{C}}{M_{C}}=\frac{36.22 g}{12 g/mol}\approx 3 mol

Similarly, number of moles of oxygen will be:

n_{O}=\frac{m_{O}}{M_{O}}=\frac{48 g}{16 g/mol}=3 mol

The ratio of number of moles of carbon and oxygen will be:

C:O=n_{C}:n_{O}=3:3=1:1

The formula of compound will be CO.

Therefore, it is proved that carbon and oxygen are present in fixed ratios in both the samples.


4 0
2 years ago
Plz help me I am!!!!
Soloha48 [4]
Gravity forces earth to move around the sun so A
8 0
2 years ago
Read 2 more answers
What is the equilibrium expression for the reaction below?
Mariana [72]

Answer:

A. K=\frac{[N_2O]^2}{[N_2]^2[O_2]}

Explanation:

Hello there!

In this case, for us to figure out the appropriate equilibrium expression, it will be firstly necessary for us to recall the law of conservation of mass which states that the equilibrium constant of an equilibrium chemical reaction is written by dividing the products and reactants and including the stoichiometric coefficients as exponents. In such a way, for the given reaction, we will have:

K=\frac{[N_2O]^2}{[N_2]^2[O_2]}

As N2O is the product whereas N2 and O2 are reactants; thus, the equilibrium expression will be A.

Regards!

6 0
2 years ago
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