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3 years ago

What is the ph of a 0.135 m aqueous solution of potassium acetate, kch3coo? (ka for ch3cooh = 1.8×10-5)?

1 answer:

6 0

[OH-] = √(Cs×Kw)/Ka
[OH-] = √(0,135×10^-14)/1,8×10^-5
[OH-] = √0,075×10^-9 = √75×10^-12 = 8,66×10^-6

pOH = -log[OH-]
pOH = -log[8,66×10^-6]
pOH ≈ 5,0625

pH + pOH = 14
pH = 14-5,0625
pH = 8,9375

:•)

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A cube made of platinum (Pt) has an edge length of 1.0 cm. (a) Calculate the number of Pt atoms in the cube. (b) Atoms are spher

irina1246 [14]

Answer:

a)The total number of platinum atoms are $6.620\times 10^{22} atoms$ .

b)The radius of a Pt atom is 138.7 pm.

Explanation:

a) Let the total number of platinum atoms be x

And mass of x atoms of platinum be m

Edge length of platinum cube ,s= 1.0 cm

Volume of the cube = $1.0 cm^3$

Density of the platinum cube = $d=21.45 g/cm^3$

Mass = Density × Volume

$(m)=21.45 g/cm^3\times 1.0 cm^3=21.45 g$

Mass of an atom of platinum = $3.240\times 10^{-22} g$

$x\times 3.240\times 10^{-22} g=21.45 g$

$x=6.620\times 10^{22} atoms$

b) If only 74 percent of the space inside the cube is taken up by Pt atoms.

Volume occupied by platinum atoms = 74% of $1.0 cm^3$

$V'= 0.74 cm^3$

Volume occupied by $6.620\times 10^{22}$ atoms is $0.74 cm^3$ .

$6.620\times 10^{22} \times \frac{4}{3}\pi r^3=V'$

$6.620\times 10^{22} \times \frac{4}{3}\times 3.14\times r^3=0.74 cm^3$

$r = 1.387\times 10^{-8} m = 138.7 pm$

The radius of a Pt atom is 138.7 pm.

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3 years ago

How many protons, neutrons, and electrons are present in an atom of hafnium, Hf, with a mass number of

Soloha48 [4]

N: 106Answer:

72 protons, 106 neutrons, 72 electrons.

Explanation:

to solve this use this simple method: APEMAN.

A= atomic number, P= Protons, E= Electrons.

M= Mass, A= atomic number, N= neutrons.

1. APE (atomic number, protons, electrons) are the same. since Hf (Hafnium) atomic number is 72, Hf has 72 protonsand ele ctrons.

2. to get Neutrons it will be mass-atomic number= neutrons.(M-A=N)

Hf mass= 178. So, 178-72= 106 neutrons.

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3 years ago

Please help brainiest is award!!!!!!!!!!!

Alekssandra [29.7K]

Answer:

it doesnt even give you enough information for you to answer it

Explanation:

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3 years ago

Read 2 more answers

HClO4 acid solution has a concentration of 5 Molarity. Calculate the concentration of this solution in

Nutka1998 [239]

Answer:

1. Percentage by weight = 0.5023 = 50.23 %

2. molar fraction =0.153

Explanation:

We know that

Molar mass of HClO4 = 100.46 g/mol

So the mass of 5 Moles= 5 x 100.46

Mass (m)= 5 x 100.46 = 502.3 g

Lets assume that aqueous solution of HClO4 and the density of solution is equal to density of water.

Given that concentration HClO4 is 5 M it means that it have 5 moles of HClO4 in 1000 ml.

We know that

Mass = density x volume

Mass of 1000 ml solution = 1 x 1000 =1000 ( density = 1 gm/ml)

m'=1000 g

Percentage by weight = 502.3 /1000

Percentage by weight = 0.5023 = 50.23 %

We know that

molar mass of water = 18 g/mol

mass of water in 1000 ml = 1000 - 502.3 g=497.9 g

So moles of water = 497.7 /18 mole

moles of water = 27.65 moles

So molar fraction = 5/(5+27.65)

molar fraction =0.153

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2 years ago

Which unit abbreviation is a measurement of force?

Artemon [7]

So,

Recall Newton's Second Law of Motion: force = mass x acceleration

Also recall:

acceleration = velocity/time
velocity = distance/time

Distance is expressed in meters.
Time is expressed in seconds.
Mass is expressed in kilograms.

v = m/s
a = m/s^2
F = m * a
F = kg * m/s^2

$F= \frac{kg*m}{s^2}$

The unit for force is the Newton (N).

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3 years ago

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