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3 years ago

Why concentrated HNO3 is 69% by mass of nitric acid? Please explain what it means.

Chemistry

1 answer:

Lyrx [107]3 years ago

7 0

Answer:

See the answer below

Explanation:

The percentage by mass of a substance in a mixture is the ratio of the mass of the substance and the mass of the entire mixture.

Hence, when concentrated HNO3 is said to be 69% by mass of nitric acid, it means that the solution of the acid has 69% HNO3 and 31% water in terms of mass. More specifically, 100 g of the solution of the acid would contain 69 g of HNO3 and 31 g of water respectively,

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What is the % dissociation of a solution of acetic acid if at equilibrium the solution has a pH = 4.74 and a pKa = 4.74?

Ymorist [56]

Answer:

$\% diss = 50\%$

Explanation:

Hello there!

In this case, when considering weak acids which have an associated percent dissociation, we first need to set up the ionization reaction and the equilibrium expression:

$HA\rightleftharpoons H^++A^-\\\\Ka=\frac{[H^+][A^-]}{[HA]}$

Now, by introducing x as the reaction extent which also represents the concentration of both H+ and A-, we have:

$Ka=\frac{x^2}{[HA]_0-x} =10^{-4.74}=1.82x10^{-5}$

Thus, it is possible to find x given the pH as shown below:

$x=10^{-pH}=10^{-4.74}=1.82x10^{-5}M$

So that we can calculate the initial concentration of the acid:

$\frac{(1.82x10^{-5})^2}{[HA]_0-1.82x10^{-5}} =1.82x10^{-5}\\\\\frac{1.82x10^{-5}}{[HA]_0-1.82x10^{-5}} =1\\\\$

$[HA]_0=3.64x10^{-5}M$

Therefore, the percent dissociation turns out to be:

$\% diss=\frac{x}{[HA]_0}*100\% \\\\\% diss=\frac{1.82x10^{-5}M}{3.64x10^{-5}M}*100\% \\\\\% diss = 50\%$

Best regards!

6 0

3 years ago

Determine the empirical and molecular formula:

Bingel [31]

Answer:

The empirical formula = molecular formula = C13H18O2

Explanation:

in 100% compound we have 75.6 % Carbon ( Molar mass = 12g/mole), 8.80% hydrogen ( Molar mass = 1.01 g/mole) and 15.5% Oxygen (Molar mass = 16.01 g/mole).

Carbon: 75.6g / 12 = 6.29

Hydrogen: 8.80/ 1 = 8.80

Oxygen: 15.5/ 16 = 0.97

⇒0.97 is the smallest so we divide everything through by 0.97

C: 6.29 / 0.97 = 6.48 ≈ 6.5

H: 8.80 /0.97 = 9

O: 0.97 / 0.97 = 1

To get rid of decimals, we multiply by 2

C: 6.5 x 2 = 13

H: 9 x 2 = 18

O: 1 x 2 = 2

The empirical formula = C13H18O2

13x 12g/mol + 18x1g/mol + 2x 16g/mol = 156 + 18 + 32 = 206g/mol which is the molar mass of ibuprofen

The empirical formula = molecular formula = C13H18O2

6 0

3 years ago

A 3" diameter germanium wafer that is 0.020" thick at 300K has 3.419*10^17 As atoms added to it. What is the resistivity of the

earnstyle [38]

They temperature in my room is 57 degrees

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3 years ago

A 46.9 gram sample of a substance has a volume of about 3.5 centimeters3. It is solid at a room temperature of 23ºC. Out of the

Masteriza [31]

Answer:- C. Hafnium.

Solution:- Mass of the sample is 46.0 g and it's volume is $3.5cm^3$ .

From mass and volume, we can calculate it's density using the formula:

$density=\frac{mass}{volume}$

$density=\frac{46.9g}{3.5cm^3}$

$density=\frac{13.4g}{cm^3}$

On the basis of the density, this substance could either be mercury or hafnium. Since the substance is a solid at room temperature where as mercury is liquid. So, it can't be mercury.

The right choice is C) Hafnium.

3 0

3 years ago

An analytical chemist is titrating 242.5mL of a 1.200M solution of hydrazoic acid HN3 with a 0.3400M solution of NaOH . The pKa

fgiga [73]

Answer: The pH of the solution is 12.61

Explanation:

To calculate the number of moles for given molarity, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution (in mL)}}$ ......(1)