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3 years ago

The metallic radius of a potassium atom is 231 pm. What is the volume of a potassium atom in cubic meters?

1 answer:

8 0

1 pm = 10∧-10 cm
Therefore, 230 pm is equivalent to 2.3 ×10∧-8 cm.
Atom is in the shape of a sphere,
The volume of a sphere is given by 4/3πr³
Thus, volume of the atom = 4/3π( 2.3 ×10∧-8)³
= 4/3 (3.142 ×12.167×10∧-24
= 5.096 ×10∧-23 cm³
but 1m³= 1000000cm³
Therefore, the volume of the atom = 5.096 ×10∧-29 m³

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Calculate the change in entropy of 3 moles of liquid water if you heat it from 5˚C to 95˚C. The molar heat capacity of liquid wa

IceJOKER [234]

<u>Answer:</u> The entropy change of the liquid water is 63.4 J/K

<u>Explanation:</u>

To calculate the entropy change for same phase at different temperature, we use the equation:

$\Delta S=n\times C_{p}\times \ln (\frac{T_2}{T_1})$

where,

$\Delta S$ = Entropy change

$C_{p}$ = molar heat capacity of liquid water = 75.38 J/mol.K

n = number of moles of liquid water = 3 moles

$T_2$ = final temperature = $95^oC=[95+273]K=368K$

$T_1$ = initial temperature = $5^oC=[5+273]K=278K$

Putting values in above equation, we get:

$\Delta S=3mol\times 75.38J/mol.K\times \ln (\frac{368}{278})\\\\\Delta S=63.4J/K$

Hence, the entropy change of the liquid water is 63.4 J/K

4 0

3 years ago

How many copper atoms are in 150 g of copper metal

GaryK [48]

1. From grams -> mole:

=grams given x 1 mol/molar mass

So 150 g Cu x 1 mol Cu/63.546 g Cu = 2.4 mol Cu

2. From mole -> atoms

=number of mol x 6.022x10^22 atoms/1 mol

So 2.4 mol Cu x 6.022x10^22 atoms Cu/1 mol Cu = 1.4 x 10^24 atoms Cu

5 0

3 years ago

During an experiment, 95 grams of calcium carbonate reacted with an excess amount of hydrochloric acid. If the percent yield of

almond37 [142]

Answer:

Actual yield: 86.5 grams.

Explanation:

How many moles of formula units in 95 grams of calcium carbonate $\rm CaCO_3$ ?

Refer to a modern periodic table for relative atomic mass data:

Ca: 40.078;
C: 12.011;
O: 15.999.

Formula mass of $\rm CaCO_3$ :

$M(\mathrm{CaCO_3}) = \underbrace{1\times 40.078}_{\rm Ca} + \underbrace{1\times 12.011}_{\rm C} + \underbrace{3\times 15.999}_{\rm O} = \rm 100.086\;g\cdot mol^{-1}$ .

$\displaystyle n(\mathrm{CaCO_3}) = \frac{m(\mathrm{CaCO_3})}{M(\mathrm{CaCO_3})} = \rm \frac{95\;g}{100.086\;g\cdot mol^{-1}} = 0.949184\;mol$ .

How many moles of $\rm CaCl_2$ will be produced?

The coefficient in front of $\rm CaCO_3$ in the chemical equation is the same as that in front of $\rm CaCl_2$ . That is:

$\displaystyle \frac{n(\rm CaCl_2)}{n(\rm CaCO_3)} = 1$ .

$\displaystyle n(\mathrm{CaCl_2}) = n(\mathrm{CaCO_3})\cdot \frac{n(\rm CaCl_2)}{n(\rm CaCO_3)} = n(\mathrm{CaCO_3}) = \rm 0.949184\;mol$ .

What's the theoretical yield of calcium chloride? In other words, what's the mass of $\rm 0.949184\;mol$ of $\rm CaCl_2$ ?

Again, refer to a periodic table for relative atomic data:

Ca: 40.078;
Cl: 35.45.

$M(\mathrm{CaCl_2}) = \underbrace{1\times 40.078}_{\rm Ca} + \underbrace{2\times 35.45}_{\rm Cl} = \rm 110.978\;g\cdot mol^{-1}$ .

$\begin{aligned}m(\mathrm{CaCl_2}) &= n(\mathrm{CaCl_2})\cdot M(\mathrm{CaCl_2})\\ &= \rm 0.949184\;mol\times 110.978\;g\cdot mol^{-1}\\ &= \rm 105.339\; g\end{aligned}$ .

What's the actual yield of calcium chloride?

$\displaystyle \text{Percentage Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}}\times 100\%$ .

$\displaystyle \begin{aligned}\text{Actual Yield} &= \text{Theoretical Yield}\cdot \frac{\text{Percentage Yield}}{100\%}\\ &=\rm 105.339\; g \times \frac{82.15\%}{100\%}\\&= \rm 86.5\;g \end{aligned}$ .

8 0

4 years ago

a skateboarder wants to skate down the ramp at a skate park he will want the forces acting on him to be

kvasek [131]

Answer:

increase

Explanation:

At the skate park when a skateboarder wants to skate down a ramp, the skate boarder wishes to move faster and with speed so that it help him to skate more time. This can only be achieved if the all the forces acting on him will increase as he skates down the ramp without much of the frictional force acting on the wheels of the skate board. The less friction force acts on the wheel, the more he can skate with more speed.

Thus, the skateboarder wants the force to be increase that is acting on him.

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3 years ago

a chemist determined by measurements that 0.015 moles of tungsten participated in a chemical reaction. Calculate the mass of tun

ICE Princess25 [194]

Answer: 0.84g

Explanation:

8 0

3 years ago