.

How many half-lives are required for three-fourths of the nuclei of an isotope in a sample to decay?

prisoha [69]

2 half lives are required.

5 0

2 years ago

If 21.00 mL of a 0.68 M solution of C6H5NH2 required 6.60 mL of the strong acid to completely neutralize the solution, what was

Andru [333]

Answer:

pH = 2.46

Explanation:

Hello there!

In this case, since this neutralization reaction may be assumed to occur in a 1:1 mole ratio between the base and the strong acid, it is possible to write the following moles and volume-concentrations relationship for the equivalence point:

$n_{acid}=n_{base}=n_{salt}$

Whereas the moles of the salt are computed as shown below:

$n_{salt}=0.021L*0.68mol/L=0.01428mol$

So we can divide those moles by the total volume (0.021L+0.0066L=0.0276L) to obtain the concentration of the final salt:

$[salt]=0.01428mol/0.0276L=0.517M$

Now, we need to keep in mind that this is an acidic salt since the base is weak and the acid strong, so the determinant ionization is:

$C_6H_5NH_3^++H_2O\rightleftharpoons C_6H_5NH_2+H_3O^+$

Whose equilibrium expression is:

$Ka=\frac{[C_6H_5NH_2][H_3O^+]}{C_6H_5NH_3^+}$

Now, since the Kb of C6H5NH2 is 4.3 x 10^-10, its Ka is 2.326x10^-5 (Kw/Kb), we can also write:

$2.326x10^{-5}=\frac{x^2}{0.517M}$

Whereas x is:

$x=\sqrt{0.517*2.326x10^{-5}}\\\\x=3.47x10^-3$

Which also equals the concentration of hydrogen ions; therefore, the pH at the equivalence point is:

$pH=-log(3.47x10^{-3})\\\\pH=2.46$

Regards!

6 0

2 years ago

How many km are in 5.6mm? 5.6x103 5.6x10-6 5.6x10-3 5.6x106

il63 [147K]

Hey there :)

Question: How many km are in 5.6mm?

=>5.6x10^3

=>5.6x10^-6

=>5.6x10^-3

=> 5.6x10^6

Answer:-

$5.6 \times 10^{ - 6}$

Explanation:-

By using the formula-

$1millimeter = \frac{1}{1000000}$

As 1 with 6 zeros, we convert it into exponential form.

$= > \frac{1}{10^{6} }$

As this above value is fraction type, we can do the reciprocal, thus, the exponent gets a negative value.

$= > 10^{ - 6}$

Now combine with given question.

$= > 5.6 \times 10^{ - 6}$

7 0

2 years ago

Which solution would most likely cause a plant placed in it to become firmer and more rigid? A. hypertonic B. hypotonic C. isoto

Anna11 [10]

"Hypotonic" is the one solution among the choices given in the question that would most likely cause a plant placed in it to become firmer and more rigid. The correct option among all the options that are given in the question is the second option or option "B". I hope the answer has come to your great help.

5 0

3 years ago

Read 2 more answers

At a certain temperature and pressure, 0.20 mol of carbon dioxide has a volume of 3.1 L. A 3.1-L sample of hydrogen at the same

Arada [10]

A 3.1 L sample of hydrogen d. contains the same number of molecules

as 3.1 L of carbon dioxide at the same temperature and pressure.

This is the fundamental principle of Avogadro’s hypothesis: equal volume of gases at the same temperature and pressure contain the same number of molecules.

The sample of carbon dioxide has a greater mass, a greater number of atoms, and a greater density, than the sample of hydrogen.

7 0

3 years ago