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2 years ago

How many formula units of CaO are in 32.7 g of CaO?

Chemistry

1 answer:

max2010maxim [7]2 years ago

7 0

Answer:

3.51× 10²³ formula units

Explanation:

Given data:

Mass of CaO = 32.7 g

Number of formula units = ?

Solution:

First of all we will calculate the number of moles.

Number of moles = mass/molar mass

Number of moles = 32.7 g/ 56.1 g/mol

Number of moles = 0.583 mol

Number of formula units:

1 mole = 6.022 × 10²³ formula units

0.583 mol × 6.022 × 10²³ formula units / 1 mol

3.51× 10²³ formula units

The number 6.022 × 10²³ is called Avogadro number.

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nataly862011 [7]

Answer:2,144.7

Explanation:

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2 years ago

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Purification of copper can be achieved by electrorefining copper from an impure copper anode onto a pure copper cathode in an el

Likurg_2 [28]

Answer: 281 hours

Explanation:-

1 electron carry charge= $1.6\times 10^{-19}C$

1 mole of electrons contain= $6.023\times 10^{23}$ electrons

Thus 1 mole of electrons carry charge= $\frac{1.6\times 10^{-19}}{1}\times 6.023\times 10^{23}=96500C$

$Cu^{2+}+2e^-\rightarrow Cu$

$96500\times 2=193000Coloumb$ of electricity deposits 1 mole or 63.5 g of copper

0.0635 kg of copper is deposited by 193000 Coloumb

11.5 kg of copper is deposited by= $\frac{193000}{0.0635}\times 11.5=34952756$ Coloumb

$Q=I\times t$

where Q= quantity of electricity in coloumbs = 34952756 C

I = current in amperes = 34.5 A

t= time in seconds = ?

$34952756 C=34.5A\times t$

$t=1013123sec=281hours$

Thus it will take 281 hours to plate 11.5 kg of copper onto the cathode if the current passed through the cell is held constant at 34.5 A.

8 0

3 years ago

Copper crystallizes in a face-centered cubic unit cell. the density of copper is 8.94 g/cm3. calculate the length of the edge of

Ilia_Sergeevich [38]

361.4 pm is the length of the edge of the unit cell. First, let's calculate the average volume each atom is taking. Start with calculating how many moles of copper we have in a cubic centimeter by looking up the atomic weight. Atomic weight copper = 63.546 Now divide the mass by the atomic weight, getting 8.94 g / 63.546 g/mol = 0.140685488 mol And multiply by Avogadro's number to get the number of atoms: 0.140685488 * 6.022140857x10^23 = 8.472278233x10^22 Now examine the face-centered cubic unit cell to see how many atoms worth of space it consumes. There is 1 atom at each of the 8 corners and each of those atoms is shared between 8 unit cells for for a space consumption of 8/8 = 1 atom. And there are 6 faces, each with an atom in the center, each of which is shared between 2 unit cells for a space consumption of 6/2 = 3 atoms. So each unit cell consumes as much space as 4 atoms. Let's divide the number of atoms in that cubic centimeter by 4 to determine the number of unit cells in that volume. 8.472278233x10^22 / 4 = 2.118069558x10^22 Now calculate the volume each unit cell occupies. 1 cm^3 / 2.118069558x10^22 = 4.721280262x10^-23 cm^3 Let's get the cube root to get the length of an edge. (4.721280262x10^-23 cm^3)^(1/3) = 3.61426x10^-08 cm Now let's convert from cm to pm. 3.61426x10^-08 cm / 100 cm/m * 1x10^12 pm/m = 361.4 pm Doing an independent search for the Crystallographic Features of Copper, I see that the Lattice Parameter for copper at at 293 K is 3.6147 x 10^-10 m which is in very close agreement with the calculated amount above. And since metals expand and contract with heat and cold, I assume the slight difference in values is due to the density figure given being determined at a temperature lower than 293 K.

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2 years ago

Which of the following is not true for an exothermic reaction?

Gennadij [26K]

Answer:

The false statement regarding an exothermic reaction is: A. the products have a higher enthalpy than reactants

Explanation:

An exothermic reaction is a type of chemical reaction that involves the release of energy from the system to the surroundings. Thus increasing the temperature of the surroundings.

In this reaction, the enthalpy or energy of the reactants is greater than the enthalpy or energy of the products. ( $\Delta H_{f} (Products) < \Delta H_{f} (reactants)$ )

As the enthalpy change of a reaction: $\Delta H_{r} = \sum \Delta H_{f} (Products) - \sum \Delta H_{f} (reactants)$

Therefore, the enthalpy change for an exothermic reaction is negative ( $\Delta H_{r} < 0$ )

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3 years ago

Draw the two chair conformations of cis 1 chloro 2 methylcyclohexane

Mrrafil [7]

In chair conformations of cyclohexane, Cl group is on the first C and methyl group is on the second C. In the cis conformation both groups should be in the same orientation, either both side chains should be up and up or down and down. In this figure its up and up.
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When A flips to B, Cl goes from axial to equatorial and CH3 goes from equatorial to axial but both remain up.

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3 years ago