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3 years ago

Chemistry help

Chemistry

1 answer:

Agata [3.3K]3 years ago

3 0

Question 3.

Answer:

They are equal in magnitude but opposite in sign.

Explanation:

Fusion is another word for melting and crystallization is another word for freezing.

They are opposite processes, so the heat you must add (positive sign) to melt a substance is equal to the heat released but with a negative sign.

ΔH(fus) = -ΔH(cryst)

===============

Question 4.

Answer:

18 400 J

Explanation:

There are two heat transfers in this question.

Total heat = heat to cool water + heat to freeze water

q = q₁ + q₂

q = mCΔT + mΔH(freeze)

Calculate q₁

m = 40.0 g

C = 4.184 J·K⁻¹g⁻¹

ΔT = T_f – T_i = 0 °C - 30 °C = -30 °C

q₁ = 40.0 × 4.184× (-30)

q₁ = -5020 J

Calculate q₂

ΔH(cryst) = -334 J·g⁻¹

q₂ = 40.0 × (-334)

q₂ = -13 360 J

Calculate the total heat

q = -5 020 – 13 360

q = - 18 400 J

The negative sign shows that heat is removed, so you must remove

18 400 J.

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When 2.69 g 2.69 g of a nonelectrolyte solute is dissolved in water to make 345 mL 345 mL of solution at 26 °C, 26 °C, the solut

Gre4nikov [31]

Answer:

The molar concentration of this solution is 0.0463 mol/L

Explanation:

Step 1 : Data given

Mass of a nonelectrolyte solute = 2.69 grams

Volume of water = 345 mL = 0.345 L

Temperature = 26.0°CC = 273 + 26 = 299 K

The osmotic pressure = 863 torr

⇒ 863torr /760 = 1.13553 atm

Step 2: Calculate the molar concentration of this solution

Π = i*M*R*T

⇒with Π = the osmotic pressure = 1.13553 atm

⇒with i = the van't Hoff factor of the nonelectrolyte solute = 1

⇒with M = the molar concentration = TO BE DETERMINED

⇒with R = the gas constant = 0.08206 L*atm/mol*K

⇒with T = the temperature = 299 K

1.13553 atm = 1 * M * 0.08206 L*atm/mol*K * 299 K

M = 1.13553 / (0.08206*299)

M = 0.0463 mol/L

The molar concentration of this solution is 0.0463 mol/L

5 0

2 years ago

COCl2(g) decomposes according to the equation above. When pure COCl2(g) is injected into a rigid, previously evacuated flask at

mestny [16]

Answer: The value of $K_p$ for the reaction at 690 K is 0.05

Explanation:

We are given:

Initial pressure of $COCl_2$ = 1.0 atm

Total pressure at equilibrium = 1.2 atm

The chemical equation for the decomposition of phosgene follows:

$COCl_2(g)\rightleftharpoons CO(g)+Cl_2(g)$

Initial: 1 - -

At eqllm: 1-x x x

We are given:

Total pressure at equilibrium = [(1 - x) + x+ x]

So, the equation becomes:

$[(1 - x) + x+ x]=1.2\\\\x=0.2atm$

The expression for $K_p$ for above equation follows:

$K_p=\frac{p_{CO}\times p_{Cl_2}}{p_{COCl_2}}$

$p_{CO}=0.2atm\\p_{Cl_2}=0.2atm\\p_{COCl_2}=(1-0.2)=0.8atm$

Putting values in above equation, we get:

$K_p=\frac{0.2\times 0.2}{0.8}\\\\K_p=0.05$

Hence, the value of $K_p$ for the reaction at 690 K is 0.05

3 0

2 years ago

How many mL of a 0.375 M solution can be made from 35 g of calcium phosphate?

andrew11 [14]

Answer:

300 mL

Explanation:

the unit formula of calcium phosphate is Ca3(PO4)2

molar mass of Ca3(PO4)2 = (3×40 + 2×31 + 8×16) g/mol = 310 g/mol

n = m/M = 35 g/(310 g/mol)

c = n/V

V = n/c = [35 g/(310 g/mol)]/0.375 mol/L

V = 0.30 L = 300 mL

3 0

2 years ago

A(n) wave carries energy through matter.

denis23 [38]

Answer:

A wave is a disturbance that carries energy from one place to another through matter and space. When we through a stone or a pebble in calm water, then the particles of water moves up and down and this process continues for some time. This implies that there is a disturbance produced in water.

Explanation:

4 0

3 years ago

If the distance between a point charge and a neutral atom and is multiplied by a factor of 5, by what factor does the force on t

dexar [7]

Given :

The distance between a point charge and a neutral atom and is multiplied by a factor of 5.

To Find :

By what factor does the force on the neutral atom by the point charge change.

Solution :

We know, electrostatic force between two object is directly proportional to product of charge and inversely proportional to distance between them.

Now, charge in neutral atom is 0 C.

So, the electrostatic force between two of them is also 0 N.

Therefore, by changing distance between the charge the forces did no change ( it remains zero).

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3 years ago