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You decided to prepare a phosphate buffer from solid sodium dihydrogen phosphate (NaH2PO4) and disodium hydrogen phosphate (Na2H

KIM [24]

Answer:

For disodium hydrogen phosphate:

5.32g Na2HPO4

For sodium dihydrogen phosphate:

7.65g Na2HPO4

Explanation:

First, you have to put all the data from the problem that you going to use:

-NaH2PO4 (weak acid)

-Na2HPO4 (a weak base)

-Volume = 1L

-Buffer pH = 7.00

-Concentration of [NaH2PO4 + Na2HPO4] = 0.100 M

What we need to find the pKa of the weak acid, in this case NaH2PO4, for that you need to find the Ka (acid constant) of NaH2PO4, and for this we use the pKa of the phosphoric acid as follow:

H3PO4 = H2PO4 + H+ pKa1 = 2.14

H2PO4 = HPO4 + H+ pKa2 = 6.86

HPO4 = PO4 + H+ pKa3 = 12.4

So, for the preparation of buffer, you need to use the pKa that is near to the value of the pH that you want, so the choice will be:

pKa2= 6.86

Now we going to use the Henderson Hasselbalch equation for the pH of a buffer solution:

pH = pKa2 + log [(NaH2PO4)/(Na2HPO4)]

The solution of the problem is attached to this answer.

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7 0

3 years ago

How many atoms of Kr (Krypton) are in a balloon that contains 2.00 mol of Kr? (4)

Svetllana [295]

Answer:

$atoms= 1.204x10^{24}atoms$

Explanation:

Hello!

In this case, according to the Avogadro's number, it is possible to compute the atoms of Kr in 2.00 moles as shown below:

$atoms=2.00mol*\frac{6.022x10^{23}atoms}{1mol} \\\\atoms= 1.204x10^{24}atoms$

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4 0

2 years ago

In each pair, choose the larger of the indicated quantities or state that the samples are equal:

romanna [79]

<u> There are more total ions in 2.2 moles of </u> $MgCl_2$

Ion, any atom or group of atoms that bears one or more positive or negative electrical charges. Positively charged ions are called cations; negatively charged ions, anions.

Ions are formed by the addition of electrons to, or the removal of electrons from, neutral atoms or molecules or other ions; by combination of ions with other particles; or by rupture of a covalent bond between two atoms in such a way that both of the electrons of the bond are left in association with one of the formerly bonded atoms.

Examples of these processes include the reaction of a sodium atom with a chlorine atom to form a sodium cation and a chloride anion; the addition of a hydrogen cation to an ammonia molecule to form an ammonium cation; and the dissociation of a water molecule to form a hydrogen cation and a hydroxide anion.

Learn more about ions

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8 0

1 year ago

A gas at 928 kpa, 129 C occupies a volume of 569 L. Calculate the volume at 319 kpa and<br> 32 C.

lisabon 2012 [21]

Answer:

1255.4L

Explanation:

Given parameters:

P₁ = 928kpa

T₁ = 129°C

V₁ = 569L

P₂ = 319kpa

T₂ = 32°C

Unknown:

V₂ = ?

Solution:

The combined gas law application to this problem can help us solve it. It is mathematically expressed as;

$\frac{P_{1} V_{1} }{T_{1} } = \frac{P_{2} V_{2} }{T_{2} }$

P, V and T are pressure, volume and temperature

where 1 and 2 are initial and final states.

Now,

take the units to the appropriate ones;

kpa to atm, °C to K

P₂ = 319kpa in atm gives 3.15atm

P₁ = 928kpa gives 9.16atm

T₂ = 32°C gives 273 + 32 = 305K

T₁ = 129°C gives 129 + 273 = 402K

Input the values in the equation and solve for V₂;

$\frac{9.16 x 569}{402} = \frac{3.15 x V_{2} }{305}$

V₂ = 1255.4L

4 0

3 years ago

Match these items. 1. moles per liter of solution solute 2. spreading out Keq 3. substance being dissolved diffusion 4. general

Degger [83]

Answer:

1. moles per liter of solution - Molarity

2. spreading out - diffusion

3. substance being dissolved- solute

4. general equilibrium constant - Keq

5. the substance doing the dissolving in a solution - solvent

6. solubility product constant - Ksp

Explanation:

Number of moles of substance being dissolved in one liter of solution is defined as molarity

Solute is the substance which is dissolved and solvent is the substance into which the solute is dissolved. For example salt is solute and water is solvent.

Ksp defines the solubility product constant which indicates the equilibrium between a solid and solution and the number of ions of solid required to achieve this equilibrium.

Keq depicts the scenario where reactant and product concentrations are constant in a chemical reaction.

Hence, the correct match is

1. moles per liter of solution - Molarity

2. spreading out - diffusion

3. substance being dissolved- solute

4. general equilibrium constant - Keq

5. the substance doing the dissolving in a solution - solvent

6. solubility product constant - Ksp

8 0

3 years ago