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3 years ago

Which of these elements is a metal? Hafnium Radon Silicon Sulfur Selenium

2 answers:

6 0

Selenium is a non metal, radon is a noble gas, silicon is a metalloid, and sulphur is a non metal. Hafnium is a transition metal.

natali 33 [55]3 years ago

6 0

Answer:

Hafnium

Explanation:

Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals

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Calculate the number of moles of Cl2 produced at equilibrium when 3.98 mol of PCl5 is heated at 283.9 deg celsius in a vessel ha

ddd [48]

Answer:

1.274 moles

Explanation:

The equation for the reaction can be represented as follows:

$PCl_5(g)$ ⇄ $PCl_3(g)$ + $Cl_2(g)$

K = 0.060

K = $\frac{[PCl_3][Cl_2]}{[PCl_5]}$

Concentration of $PCl_5(g)$ = $\frac{numbers of moles}{volume}$

Concentration of $PCl_5(g)$ = $\frac{3.98}{10.0}$

Concentration of $PCl_5(g)$ = 0.398 moles

If we construct an ICE table for the above equation; we have:

$PCl_5(g)$ ⇄ $PCl_3(g)$ + $Cl_2(g)$

Initial 0.398 0 0

Change - x + x + x

Equilibrium (0.398 - x) x x

K = $\frac{[PCl_3][Cl_2]}{[PCl_5]}$

K = $\frac{[x][x]}{[0.398-x]}$

K = $\frac{x^2}{0.398-x}$

0.060 = $\frac{x^2}{0.398-x}$

0.06(0.398-x) = x²

0.02388 - 0.060x = x²

x² + 0.060x - 0.02388 = 0 (quadratic equation)

a = 1; b= 0.06; c= -0.02388

Using quadratic formula;

= $\frac{-b+/-\sqrt{b^2-4ac} }{2a}$

= $\frac{-0.06+/-\sqrt{(0.06)^2-4(1)(-0.02388)} }{(2*1)}$

= $\frac{-0.060+/-\sqrt{0.0036+0.09552} }{2}$

= $\frac{-0.06+/-\sqrt{0.09912} }{2}$

= $\frac{-0.06+/-0.3148}{2}$

= $\frac{-0.060+0.3148}{2}$ or $\frac{-0.060-0.3148}{2}$

= $\frac{0.2548}{2}$ or $\frac{-0.3748}{2}$

= 0.1274 or -0.1874

We go by the positive value which says:

[x] = 0.1274 M

number of moles = 0.1274 × 10.0

= 1.274 moles

∴ the number of moles of Cl₂ produced at equilibrium = 1.274 moles

7 0

3 years ago

2000 km/sec. Convert that to<br> m/sec.

koban [17]

Answer:

2000 km/sec

1km=1000m

2000×1000

2000,000 m/sec

4 0

3 years ago

Atoms that have a full outer level combine with other atoms. Is this true or false

aev [14]

Answer:

false

Explanation:

some atoms already have a full outer level

8 0

3 years ago

Read 2 more answers

A plastic 2L soda bottle is flexible enough that the volume of the bottle can change even without opening it. If you have an emp

Aneli [31]

Answer: The new volume be if you put it in your freezer is 1.8 L

Explanation:

To calculate the final temperature of the system, we use the equation given by Charles' Law. This law states that volume of the gas is directly proportional to the temperature of the gas at constant pressure.

Mathematically,

$\frac{V_1}{T_1}=\frac{V_2}{T_2}$