All categories

3 years ago

What is the pH of a solution of 0.600 M K2HPO4, potassium hydrogen phosphate?

2 answers:

5 0

When pKas of polyprotic intermediates have a difference of 2 or more you just average them using the equation: pH = (pKa2 + pKa3) / 2 
pKa2 = -log(Ka2) ; pKa3 = -log(Ka3) 
so, for this problem, REGARDLESS OF THE CONCENTRATION GIVEN, the answer is: 
pH = (7.2076+12.3767) / 2 
pH = 9.79

liraira [26]3 years ago

4 0

Answer:

9.8

Explanation:

The salt K₂HPO₄ will dissociate to form the ions K⁺ and HPO₄⁻², and because of the stoichiometry of the dissociation (1:2:1) [HPO₄⁻²] = 0.600 M. So, two reactions may happen:

HPO₄⁻² + H₂O ⇄ H₂PO₄⁻ + OH⁻

HPO₄⁻² + H₂O ⇄ PO₄⁻³ + OH⁻

H₃PO₄ is a polyprotic acid and have the values of pKa:

pKa1 = 2.15

pKa2 = 7.21

pKa3 = 12.4

In this case, the second and the third equilibrium are presented, thus, the pH depends only on the pKa values, and it will be:

pH = (1/2)*(pKa2 + pKa3)

pH = (1/2)*(7.21 + 12.4)

pH = 9.8

You might be interested in

Which of the following describes metallic character on the periodic table? Question 1 options: A) It increases as you move right

Ilia_Sergeevich [38]

Answer:

Explanation:

Metallic character decreases as you move across a period in the periodic table from left to right. This occurs as atoms more readily accept electrons to fill a valence shell than lose them to remove the unfilled shell. Metallic character increases as you move down an element group in the periodic table. This is because electrons become easier to lose as the atomic radius increases, where there is less attraction between the nucleus and the valence electrons because of the increased distance between them.

3 0

2 years ago

A covalent chemical bond is one in which

vitfil [10]

I think the answer is c

4 0

2 years ago

Which best represents a homogeneous mixture of an element and a compound.

Allushta [10]

Answer:

The composition of air this is because it vmade up of oxygen, nitrogen, Nobel gages and Carbon dioxide

3 0

2 years ago

How many moles of sodium carbonate are contained by 57.3g of sodium carbonate

Lady_Fox [76]

Answer:

$\boxed {\boxed {\sf 0.541 \ mol \ Na_2CO_3}}$

Explanation:

We are asked to find how many moles of sodium carbonate are in 57.3 grams of the substance.

Carbonate is CO₃ and has an oxidation number of -2. Sodium is Na and has an oxidation number of +1. There must be 2 moles of sodium so the charge of the sodium balances the charge of the carbonate. The formula is Na₂CO₃.

We will convert grams to moles using the molar mass or the mass of 1 mole of a substance. They are found on the Periodic Table as the atomic masses, but the units are grams per mole instead of atomic mass units. Look up the molar masses of the individual elements.

Na: 22.9897693 g/mol
C: 12.011 g/mol
O: 15.999 g/mol

Remember the formula contains subscripts. There are multiple moles of some elements in 1 mole of the compound. We multiply the element's molar mass by the subscript after it, then add everything together.

Na₂ = 22.9897693 * 2= 45.9795386 g/mol
O₃ = 15.999 * 3= 47.997 g/mol
Na₂CO₃= 45.9795386 + 12.011 + 47.997 =105.9875386 g/mol

We will convert using dimensional analysis. Set up a ratio using the molar mass.

$\frac {105.9875386 \ g \ Na_2CO_3}{1 \ mol \ Na_2CO_3}$

We are converting 57.3 grams to moles, so we multiply by this value.

$57.3 \ g \ Na_2CO_3} *\frac {105.9875386 \ g \ Na_2CO_3}{1 \ mol \ Na_2CO_3}$

Flip the ratio so the units of grams of sodium carbonate cancel.

$57.3 \ g \ Na_2CO_3} *\frac {1 \ mol \ Na_2CO_3}{105.9875386 \ g \ Na_2CO_3}$

$57.3 } *\frac {1 \ mol \ Na_2CO_3}{105.9875386 }$

$\frac {57.3 }{105.9875386 } \ mol \ Na_2CO_3$

$0.5406295944 \ mol \ Na_2CO_3$

The original measurement of moles has 3 significant figures, so our answer must have the same. For the number we found that is the thousandth place. The 6 in the ten-thousandth place to the right tells us to round the 0 up to a 1.

$0.541 \ mol \ Na_2CO_3$

There are approximately 0.541 moles of sodium carbonate in 57.3 grams.

6 0

2 years ago

What is the Molar Mass of methylammonium bromide: Use the Periodic Table and round to the nearest hundredths.

egoroff_w [7]

The molar mass of methylammonium bromide is 111u.

<h3>What is molar mass?</h3>

The molar mass is defined as the mass per unit amount of substance of a given chemical entity.

Multiply the atomic weight (from the periodic table) of each element by the number of atoms of that element present in the compound.

Add it all together and put units of grams/mole after the number.

Atomic weight of H is 1u

Atomic weight of N is 14u

Atomic weight of C is 12u

Atomic weight of Br is 79u

Calculating molar mass of $2H_3NCH_3Br$ =2(1 x3+ 14+12+ 1 x 3 +79) = 111u

Hence, the molar mass of methylammonium bromide is 111u.

Learn more about molar mass here:

brainly.com/question/12127540

#SPJ1

8 0

1 year ago