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lana [24]
3 years ago
15

Merits of modern periodic table?​

Chemistry
1 answer:
ANEK [815]3 years ago
6 0

Answer:

<h3>Merits of modern periodic table:</h3>
  • The wrong position of some elements like argon, potassium, cobalt and nickel due to atomic weights have been solved by arranging the elements in the order of increasing atomic number without changing their own places.
  • The isotopes of some element have the same atomic numbers. Therefore, they find the same position in periodic table.
  • It separates metals from non-metals.
  • The groups of the table are divided into sub groups A and B due to their dissimilar properties which make the study of elements specific and easier.
  • The representative and transition elements have been separated.

Hope this helps...

Good luck on your assignment...

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Which of the following represents the least number of molecues?
Mars2501 [29]

Answer:

Answer: a) 20g of H2O (18.02 g/mol) molecules=6.68x10^23

Explanation:

In order to find the amount of molecules of each of the options, we need to follow the following equation.

molecules=\frac{mass(g)x6.022x10^{23}(molecules/mol) }{atomic weight(g/mol)}

So, let´s get the number of molecules for each of the options.

a) molecules=\frac{20(g)x6.022x10^{23}(molecules/mol) }{18.02(g/mol)}=6.68x10^{23}molecules

b) molecules=\frac{77(g)x6.022x10^{23}(molecules/mol) }{16.06(g/mol)}=2.89x10^{24}molecules

c) molecules=\frac{68(g)x6.022x10^{23}(molecules/mol) }{42.09(g/mol)}=9.73x10^{23}molecules

d) molecules=\frac{100(g)x6.022x10^{23}(molecules/mol) }{44.02(g/mol)}=1.37x10^{24}molecules

d) molecules=\frac{84(g)x6.022x10^{23}(molecules/mol) }{20.01(g/mol)}=2.53x10^{24}molecules

the smalest number is in option a)

Best of luck.

7 0
3 years ago
A flashlight battery is an example of a
kompoz [17]
<span>Dry cell battery

When an automotive battery is fully charged, the sulfuric acid and water mixture will have a specific gravity of about 1.3. Specific gravity is actually the difference in the weight of water in comparison to a specific fluid. It is measured by a hydrometer. The amount of charge in the battery is normally measured by the specific gravity of the battery. The specific gravity of water is 1 and anything less than one is considered less dense while anything that has a specific gravity of more than 1 is considered more dense than water. </span>
7 0
3 years ago
5. A beam of photons with a minimum energy of 222 kJ/mol can eject electrons from a potassium surface. Estimate the range of wav
torisob [31]

Answer: The range of wavelengths of light that can be used to cause given phenomenon is 8.953 \times 10^{21} m.

Explanation:

Given: 222 kJ/mol (1 kJ = 1000 J) = 222000 J

Formula used is as follows.

E = \frac{hc}{\lambda}

where,

E = energy

h = Planck's constant = 6.625 \times 10^{-25} Js

c = speed of light = 3 \times 10^{8} m/s

Substitute the values into above formula as follows.

E = \frac{hc}{\lambda}\\222000 J = \frac{6.625  \times 10^{-34}Js \times 3 \times 10^{8} m/s}{\lambda}\\\lambda = 8.953 \times 10^{21} m

Thus, we can conclude that the range of wavelengths of light that can be used to cause given phenomenon is 8.953 \times 10^{21} m.

7 0
3 years ago
Calculate the OH− concentration after 53 mL of the 0.100 M KOH has been added to 25.0 mL of 0.200 M HBr. Assume additive vol- um
Andre45 [30]

Answer:

\large \boxed{\text{0.0038 mol/L}}

Explanation:

1. Calculate the initial moles of acid and base

\text{moles of acid} = \text{0.0250 L} \times \dfrac{\text{0.200 mol}}{\text{1 L}} = \text{0.005 00 mol}\\\\\text{moles of base} = \text{0.053 L} \times \dfrac{\text{0.100 mol}}{\text{1 L}} = \text{0.0053 mol}

2. Calculate the moles remaining after the reaction

                   OH⁻     +     H₃O⁺ ⟶ 2H₂O

I/mol:      0.0053       0.005 00

C/mol:    -0.00500   -0.005 00

E/mol:      0.0003              0

We have an excess of 0.0003 mol of base.

3. Calculate the concentration of OH⁻

Total volume = 53 mL + 25.0 mL = 78 mL = 0.078 L

\text{[OH}^{-}] = \dfrac{\text{0.0003 mol}}{\text{0.078 L}} = \textbf{0.0038 mol/L}\\\\\text{The final concentration of OH$^{-}$ is $\large \boxed{\textbf{0.0038 mol/L}}$}

8 0
3 years ago
A student weighs out a 6.64 g sample of , transfers it to a 500. mL volumetric flask, adds enough water to dissolve it and then
Vsevolod [243]

Answer:

the molarity of cobalt(II) fluoride in the resulting solution is = 0.137  M

Explanation:

Given that :

a student dissolves 6.64 g of CoF₂  into 500 mL of water

volume of the solution(water) = 500 mL = 0.50 L

The standard  molar mass of CoF₂ is 96.93 g/mol

number of moles of CoF₂ = mass of CoF₂/molar mass of CoF₂

number of moles of CoF₂ = 6.64 g/96.93 g/mol

number of moles of CoF₂ = 0.0685 mol

The molarity of any given substance is known to be as the number of moles of solute dissolved in one litre of solution.

Thus ;

Molarity of  cobalt(II) fluoride CoF₂ in the resulting solution is = number of moles / Volume in (L)

Molarity of  cobalt(II) fluoride CoF₂  = 0.0685 mol/ 0.50 L

= 0.137  M

Thus ; the molarity of cobalt(II) fluoride in the resulting solution is = 0.137  M

7 0
3 years ago
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