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cestrela7 [59]
4 years ago
6

There are two kinds of elements that didn't appear on the periodic table until after 1892. What kinds are they and why do you th

ink it took so long to discover them?
Chemistry
2 answers:
rosijanka [135]4 years ago
6 0

Answer:

The two elements are Argon and Helium .

They are noble gas  and are not reactive

Explanation:

The two kinds of element are argon and helium. These two element were discovered in 1892 by a Scottish chemist Williams Ramsay.

These two elements are known as noble gas or inert gas  because of how hard they find it to react with other elements.

Elements back then were discovered through their reactivity with other elements but It took so long to discover these elements(argon and helium) because of their unreactive nature . Combine with the fact that they were odorless, tasteless and colorless it was more hard to discover them.

Lelu [443]4 years ago
5 0

Your Question: There are two kinds of elements that didn't appear on the periodic table until after 1892. What kinds are they and why do you think it took so long to discover them?

The Answer: Moseley’s analysis enabled chemists to refine the table further  and reveal more gaps, which suggested that there were more new  elements waiting to be discovered, with atomic numbers 43, 61, 72  and 75. Scientists subsequently found these elements—now  known as technetium, promethium, hafnium and rhenium,  respectively.

Explanation: Physicist Henry Moseley discovered the atomic number of each element using x-rays, which led to more accurate organization of the periodic table. We will cover his life and discovery of the relationship between atomic number and x-ray frequency, known as Moseley's Law.

Remember to read study guides, lessons and notes to rely yourself on; key to success is working hard. Good Luck!

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When 412.5g of calcium carbonate react with 521.9g of aluminum fluoride,how many grams of each product can be produced
aliya0001 [1]
<h3><u>Answer;</u></h3>

321.8 g CaF2

321.5 g Al2(CO3)3

<h3><u>Explanation;</u></h3>

The equation for the reaction is;  

3 CaCO3 + 2 AlF3 → 3 CaF2 + Al2(CO3)3  

Number of moles of CaCO3 will be;

=(412.5 g CaCO3) / (100.0875 g CaCO3/mol)

= 4.12139 mol CaCO3  

Number of moles of AlF3 will be;

= (521.9 g AlF3) / ( 83.9767 g AlF3/mol)

= 6.21482 mol AlF3

But;

4.12139 moles of CaCO3 would react completely with 4.12139 x (2/3) = 2.74759 moles of AlF3.

Thus; there is more AlF3 present than that, so AlF3 is in excess, and CaCO3 is the limiting reactant.  

Therefore;

Mass of CaF2 will be;

(4.12139 mol CaCO3) x (3/3) x (78.0752 g CaF2/mol) = 321.8 g CaF2  

Mass of Al2(CO3)3 on the other hand will be;

(4.12139 mol CaCO3) x (1/3) x (233.9903 g Al2(CO3)3/mol) = 321.5 g Al2(CO3)3

3 0
4 years ago
Write the charge balance for an aqueous solution of arsenic acid, H3AsO4, in which the acid can dissociate to H2AsO24 , HAsO24 2
lilavasa [31]

Answer:

Kindly check the explanation section.

Explanation:

When the Arsenic acid,H3AsO4 is put in water it dissociates to form or give out 1 proton, 2 protons or 3 protons that is 1H^+, 2H^+ and 3H^+. Check the equation showing the dissociation reactions as given below;

H3AsO4 ===========> H^+ + AsO4^-

H3AsO4 ===========> 2H^+ + AsO4^2-

H3AsO4 ===========> 3H^+ + AsO4^3-

Therefore, the total charge balance is given as:

[H^+] =[OH^-] + [ AsO4^-] + 2[ AsO4^2-] + 3[ AsO4^3-].

Kindly note that the [OH^-] is from water.

8 0
3 years ago
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Radda [10]

Answer:

Predict the glaciers' locations.

Explanation:

You must research each glacier, and where it is now. Then try to figure out where it will go. Glaciers can go either forward or backwards, but they move in patterns. Predict!

6 0
3 years ago
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which of the following groups use accounting information a.the tax department. b.business owners. c.investor. d.all of above​
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Answer:

D

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