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Shalnov [3]
3 years ago
12

how was it possible that Mendeleev was able to predict the properties of elements that no one knew about

Chemistry
1 answer:
andrew-mc [135]3 years ago
7 0
<span>He used the patterns he found in properties of known elements to predict the properties of unknown elements.</span>
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What is the definition of thermal expansion
MissTica

Answer:

Thermal expansion is the tendency of matter to change its shape, area, and volume in response to a change in temperature.

Explanation:

8 0
4 years ago
People often think bonds store or hold energy. If that is true, should the energy be high or low when a bond forms?
marta [7]

Answer:

The energy should be high.

Explanation:

Bonds do store energy and release it depending if it's endothermic or exothermic. The energy should be low because when a bond forms (endothermic) it releases heat, which helps form bonds. Having a high energy means the bond is absorbing energy, which helps break bonds (endothermic). How this helps!

4 0
3 years ago
The neutralization of a 0.455 g sample of recrystallized aspirin required 38.6 mL of 0.100 M NaOH solution. An additional 25.0 m
Schach [20]

Answer:

E) Two of the above statements are true.

Explanation:

The options are:

A) Before the solution is titrated with HCl it is pink and when the color changes from pink to colorless, the moles of H*(aq) equals the moles of OH"(aq) used in the hydrolysis of the neutralized aspirin. <em>TRUE. </em>Before the solution is titrated, there is an excess of NaOH (Basic solution, phenolphtalein is pink). Then, at equivalence point, after the addition of HCl, the pH is acidic and phenolphtalein is colorless.

B) Before the solution is titrated with HCl it is colorless and when the color changes from colorless to pink, the moles of H*(aq) equals the excess moles of OH(aq) added. <em>FALSE. </em>As was explained, before the titration, the solution is pink.

C) 25.0 mL of 0.100 M NaOH was added to the sample to hydrolyze the neutralized aspirin in the solution. The titration with HCl allows us to determine the moles of excess OH(aq) added. Once we determine the moles of excess OH(aq), we can determine moles of OH"(aq) used in the hydrolysis of the neutralized aspirin, which is equal to the moles of aspirin in the recrystallized aspirin. <em>TRUE. </em>Aspirin requires an excess of base (NaOH) for a complete dissolution (Hydrolysis). Then, we add H+ as HCl to know the excess moles of OH-. As we know the added moles of OH-, we can find the moles of OH that reacted = Moles of aspirin.  

D) We can determine the moles of aspirin in the recrystallized aspirin by titrating with the 0.100 M NaOH to the neutralization point. The purpose of the hydrolysis of the neutralized aspirin and the back-titration with the 0.100 M HCl is to confirm the moles of aspirin in the recrystallized aspirin. <em>FALSE. </em>NaOH can be added directly unyil neutralization point because, initially, aspirin can't be dissolved completely

E) Two of the above statements are true. <em>TRUE</em>

<em></em>

Right option is:

<h3>E) Two of the above statements are true.</h3>
3 0
3 years ago
Determine the number of neutrons in an atom U-233.
alexdok [17]
We Know, Atomic number of Uranium = 92
Molar mass in given species = 233

Now, Molar mass = Number of Protons + Number of Neutrons
233 = 92 + x
x = 233 - 92
x = 141

So, your final answer is 141

Hope this helps!
5 0
3 years ago
Read 2 more answers
Hydro caloric acids + calcium =
tangare [24]

That produces hydrogen gas.

4 0
3 years ago
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