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klasskru [66]
3 years ago
15

Correct answer. 9. The mass number of an element is the number of? ​

Chemistry
1 answer:
Elis [28]3 years ago
4 0

Answer:

The mass number is defined as the total number of protons and neutrons in an atom. The number of neutrons = mass number − atomic number.

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According to Le Châtelier's principle, a system at equilibrium will respond to a stress by shifting in the direction that reliev
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Answer:

a. reduces the stress

Explanation:

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4 years ago
A lab technician mixed a 550 ml solution of water and alcohol. if​ 3% of the solution is​ alcohol, how many milliliters of alcoh
kupik [55]

The solution 550 ml total and first we will find the amount of alcohol. 3% = 0.03 550 ml x .03 = 16.5 ml alcohol
 Then to find the amount of water used, we just have to subtract the amount of alcohol from the total volume  
550 ml total - 16.5 ml alcohol = 533.5 ml water
5 0
4 years ago
A sample is decomposed in the laboratory and found that it contains 52.2% carbon (C), 13.0% hydrogen (H), and 34.8% oxygen (O).
Andrej [43]
The empirical formula would be C2H6O
7 0
4 years ago
5. What concentration of acid must be added to change the pH of 1 mM phosphate buffer from 7.4 to 7.3 (pKas of the phosphate buf
mr_godi [17]

Explanation:

According to the Henderson-Hasselbalch equation, the relation between pH and pK_{a} is as follows.

               pH = pK_{a} + log \frac{base}{acid}

where,     pH = 7.4 and pK_{a} = 7.21

As here, we can use the pK_{a} nearest to the desired pH.

So,      7.4 = 7.21 + log \frac{base}{acid}

             0.19 = log \frac{base}{acid}

            \frac{base}{acid} = 1.55

1 mM phosphate buffer means [HPO_{4}] + [H_{2}PO_{4}] = 1 mM

Therefore, the two equations will be as follows.

           \frac{HPO_{4}}{H_{2}PO_{4}} = 1.55 ............. (1)

  [HPO_{4}] + [H_{2}PO_{4}] = 1 mM ........... (2)        

Now, putting the value of [HPO_{4}] from equation (1) into equation (2) as follows.

             1.55[H_{2}PO_{4}] + [tex][H_{2}PO_{4}] = 1 mM

                        2.55 [H_{2}PO_{4}] = 1 mM

                             [H_{2}PO_{4}] = 0.392 mM

Putting the value of [H_{2}PO_{4}] in equation (1) we get the following.

                     0.392 mM + [HPO_{4}] = 1 mM

                          [HPO_{4}] = (1 - 0.392) mM

                              [HPO_{4}] = 0.608 mM

Thus, we can conclude that concentration of the acid must be 0.608 mM.

7 0
3 years ago
Using the phase diagram for H2O, which of the following correctly describes water at 0°C and 1 atm?
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At the melting point. Draw a line up from 0 degrees and a line to the right from 1 atm. They meet at the line between solid and liquid... the melting point

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