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3 years ago

What is the component concentration ratio, [no2−]/[hno2], of a buffer that has a ph of 3.90? (ka of hno2 = 7.1 × 10−4)?

1 answer:

8 0

According to Henderson–Hasselbalch Equation,

pH = pKa + log [Nitrate] / [Nitric Acid]

As, Ka of Nitric Acid = 7.1 × 10⁻⁴
So,
pKa = -log [ 7.1 × 10⁻⁴ ]

pKa = 3.148

So, pH = 3.148 + log [Nitrate] / [Nitric Acid]

3.90 = 3.148 + log [Nitrate] / [Nitric Acid]

3.90 - 3.148 = log [Nitrate] / [Nitric Acid]

0.752 = log [Nitrate] / [Nitric Acid]

Taking Antilog on both sides,

[Nitrate] / [Nitric Acid] = 5.64

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Elements donate 2 electron to produce a cation with a 2+ charge

hammer [34]

Answer: alkaline earth metals (group-IIA)

Explanation:

The element which donates the electron is known as electropositive element and forms a positively charged ion called as cation. The element which accepts the electrons is known as electronegative element and forms a negatively charged ion called as anion.

Alkaline earth metals donate 2 valence electrons to acquire noble gas configuration.

For example: Berrylium is the first alkaline earth metal with atomic number of 4 and thus has 4 electrons

Electronic configuration of berrylium:

$[Be]:4:1s^22s^2$

Berrylium atom will loose two electrons to gain noble gas configuration and form berrylium cation with +2 charge.

$[Be^{2+}]:2:1s^2$

Thus Elements donate 2 electron to produce a cation with a 2+ charge are alkaline earth metals.

5 0

3 years ago

A 0.20 M solution of a weak acid has a pH of 5.40. What is the Ka for the acid?

sweet [91]

Answer:

The Ka for this weak acid is 7,92 * 10^-11

Explanation:

First of all, let's think the equation

HA + H2O <------> H3O+ + A-

When we add water to a weak acid, it dissociates in an equilibrium to generate the corresponding anion and the hydronium cation (the acid form of water)

How do you calculate Ka?? Ka is the acid equilibrium constant.

( [H3O+] . [A-] ) / [HA] where all the concentrations are in equilibrium.

We don't have the concentration in equilibrium but we have the initial concentration. So...

HA + H2O <------> H3O+ + A-

initial- 0.2 M I don't have H3O+, either A-

reaction - an specific amount reacted (X)

in equilibrium (0,2 - X) <-----> X + X

And now, how's the formula for Ka

( [H3O+] . [A-] ) / [HA] = Ka

(X . X) / (0.2-X)

X^2 / (0.2-X) = Ka

Look, that we don't have X as the [H3O+] but we know the pH, so we can know the [H3O+] indeed.

10^-pH = [H3O+]

10^-5,40 = 3,98 * 10^-6

Let's go back to Ka

( [H3O+] . [A-] ) / [HA] = Ka

(3,98 * 10^-6)^2 / (0.2 - 3,98 * 10^-6) = Ka

(3,98 * 10^-6 is an small number, soooo small that we can approximate to 0)

If we have in order 10^-6, 10^-5 we can consider that.

So now, we have

(3,98 * 10^-6)^2 / (0.2) = Ka

1,58 * 10^-11 / (0.2) = Ka = 7,92* 10^-11

5 0

3 years ago

What will happen when a star loses so much mass that its gravity becomes weaker? O A. The star will get hotter O B. The star wil

faust18 [17]

Answer: C

Explanation:

6 0

3 years ago

Phenylpyruvic acid is produced in the body of abnormal amounts as the result of a molecular disease called phenylketonuria, whic

Andrej [43]

Answer:

6. C3H2O

Explanation:

C= 12.0107; H= 1.00797; O=15.9994

We calculate:

C= 65.85/12.01=5.48

H= 4.91/1.00=4.91

O=29.24/16.00= 1.82

Later, we divide among the smaller quantity

C=5.48/1.82= 3.01

H=4.91/1.82= 2.70

O=1.82/1.82=1

8 0

3 years ago

An electrically neutral atom of gallium has 31 electrons and 39 neutrons. What is the mass number of the atom?

ollegr [7]

31 electrons + 39 neutrons = 70

7 0

3 years ago