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alex41 [277]
3 years ago
11

If you chip a tooth, most likely you will go to the dentist to have the missing material filled in. Currently the material used

to fill in teeth is a polymer that is flexible when put in, yet is hardened to the strength of a tooth after irradiation with blue light at a wavelength of 461 nm. What is the energy in Joules for a photon of light at this wavelength?
Chemistry
1 answer:
AnnZ [28]3 years ago
7 0

ti\his answer is radiation

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A sample of ideal gas is in a sealed container. The pressure of the gas is 705 torr , and the temperature is 19 ∘C . If the temp
posledela
808.77torr or 1.064atm
8 0
3 years ago
What is the sum of 2.7 g and 2.47g expressed in the correct number of significant digits
NeTakaya
In order to get the sum of 2.7 and 2.47, we will add both numbers. So, 2.7 plus 2.47 would be 5.17. And the correct number of significant digits in this number is still the same, 5.17, so we have three significant numbers. Why? There are three rules in identifying the significant figures: 1. Non zeros are always significant (which this applies in our sum above). 2. Any zeros in between significant numbers are always significant. 3. <span> The final zero or zeros in the decimal portion only are significant.</span>
5 0
3 years ago
Read 2 more answers
For the generic equilibrium HA(aq) ⇌ H+(aq) + A−(aq), which of these statements is true? For the generic equilibrium , which of
timama [110]

<u>Answer:</u> The correct statement is if you add the soluble salt KA to a solution of HA that is at equilibrium, the pH would increase.

<u>Explanation:</u>

Common ion effect is defined as the effect which occurs on equilibrium when a common ion (an ion which is already present in the solution) is added to a solution. This effect generally decreases the solubility of a solute.

Equilibrium reaction of HA and KA follows the equation:

HA\rightleftharpoons H^{+}(aq.)+A^{-}(aq.)

KA\rightleftharpoons K^+(aq.)+A^{-}(aq.)

According to Le-Chateliers principle, if there is any change in the variables of the reaction, the equilibrium will shift in the direction in order to minimize the effect.

In the equilibrium reactions, A^- ion is getting increased on the product side, so the equilibrium will shift in the direction to minimize this effect, which is in the direction of HA.

Thus, the addition of KA will shift the equilibrium in the left direction.

Equilibrium constant depends on the temperature of the system. It does not have any effect on any change of pH.

pH is defined as the negative logarithm of hydrogen ions present in the solution

  • If the solution has high hydrogen ion concentration, then the pH will be low.
  • If the solution has low hydrogen ion concentration, then the pH will be high.

As, the equilibrium is shifting in the left direction, that means concentration of H^+ ions are getting decreases. This will increase the pH of the solution.

Hence, the correct statement is if you add the soluble salt KA to a solution of HA that is at equilibrium, the pH would increase.

8 0
3 years ago
hat is the percentage of water in the following compound? Answer using three significant figures. Sodium carbonate decahydrate,
BigorU [14]
You need to find the whole molar mass of the compound using the periodic table to add the values. 

Na2CO3= (2 x 23.0) + 12.0 + (3 x 16.0)= 106 g/mol
H2O= 10 x [ (2 x 1.01 ) + (16.0) ]= 180.2 g/mol

the total molar mass is 106 + 180.2 = 286.2 g/mol

the percentage of water you can find by doing "parts over the whole"

H2O%= 180.2 / 286.2 X 100= 63.0%
7 0
3 years ago
Calculate the value of the equilibrium constant, Kc , for the equilibrium shown below, if 0.124 moles of NO, 0.0240 mole of H2,
sdas [7]

the reaction is

2NO(g) + 2H2(g) <—> N2(g) + 2H2O (g)

Kc = [N2] [ H2O]^2 / [NO]^2 [ H2]^2

Given

moles of NO = 0.124 therefore [NO] = moles /volume = 0.124 /2 = 0.062

moles of H2 = 0.0240 , therefore [H2] = moles / volume = 0.0240 / 2 = 0.012

moles of N2 = 0.0380 , therefore [N2] = moles / volume = 0.0380 / 2 = 0.019

moles of H2O  = 0.0276 , therefore [H2O] = moles / volume = 0.0276 / 2 = 0.0138

Kc = (0.019) ( 0.0138)^2 / (0.062)^2 ( 0.012)^2 = 6.54



4 0
3 years ago
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