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Irina18 [472]
3 years ago
7

What did scientists discover when they arranged elements in order of increasing atomic mass?

Chemistry
1 answer:
asambeis [7]3 years ago
4 0
<span>The scientists discovered that when they organized elements in order of increasing atomic mass there is a pattern of repetition of properties (A). The periodic law was developed by Dmitri Mendeleev and Lothar Mayer in 1869. They worked independently of each other and both created a periodic table. They both arranged the items on the table by weight and both suggested that certain properties of the elements recur. The Mendeleev table is the most important table because the values for the atomic mass are the most accurate.</span>
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A student mixed 50 ml of 1.0 M HCl and 50 ml of 1.0 M NaOH in a coffee cup calorimeter and calculated the molar enthalpy change
MrRa [10]

Answer:

-54 kJ/mol

Explanation:

Given that:

A student mixed 50 ml of 1.0 M HCl and 50 ml of 1.0 M NaOH in a coffee cup calorimeter and calculated the molar enthalpy change of the acid-base neutralization reaction to be –54 kJ/mol

i.e

50 ml of 1.0 M HCl +  50 ml of 1.0 M NaOH -----> -54 kJ/mol

If he repeat the same experiment with :

100 ml of 1.0 M HCl + 100 ml of 1.0 M NaOH. ------> ????

From The experiment; the molar enthalpy of change of the acid-base neutralization reaction will be -54 kJ/mol

This is because : The second reaction requires 50 ml in order to neutralize the reaction, then the remaining 50 ml will be excess, Hence, there is no change in the enthalpy of the reaction.

Similarly; we can assume that :

In the first reaction;  P moles of  is used to liberate Q kJ heat ; then  the change in molar enthalpy will be Q/P (kJ/mol).

SO; when he used 100 ml ;

then the amount of moles used is double, likewise the heat liberated will be doubled ;

So;

2P moles is used to liberate 2Q kJ heat ;

2P/2Q = Q/P ( kJ/mol) = -54 kJ/mol

8 0
3 years ago
How heat moves from one end of a solid to another
pantera1 [17]
In conduction, the thermal energy of a particle is transferred to other particles throughout the solid. The particles with more energy are transferred to those with less.
3 0
4 years ago
Write a chemical equation for the acid-base reaction that occurs when p-phenetidine is dissolved in hcl. why is
melisa1 [442]
<h3><u>Answer;</u></h3>

EtO-PHE-NH2 + H+ _______ EtO-PHE-NH3+ Cl-

<h3><u>Explanation;</u></h3>
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  • HCl is used for the acid-base reaction in p-phenetidine in amide synthesis of acetophenetidin rather than water becuase HCl's polarity contributes to a reaction driven to the right. It protonates the amine group, making it easy to dissolve.
6 0
3 years ago
Exam number: 007170RR
AleksandrR [38]

Answer:

A open

Explanation:

I am not sure but i think it is!

5 0
3 years ago
Mineral oil dissolves in hexane but not in ethanol
chubhunter [2.5K]
That would be correct as stated.
6 0
4 years ago
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