<h3>
Answer: Si (choice D)</h3>
This is the element Silicon.
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Explanation:
First convert each percentage to its decimal form.
For example, 92.2297% converts to 0.922297 after moving the decimal point two spots to the left.
After doing that, multiply those decimal values with their respective atomic mass unit (amu) values.
- 27.9769 * 0.922297 = 25.8030109393
- 28.9765 * 0.046832 = 1.357027448
- 29.9738 * 0.030872 = 0.9253511536
Then we add up the results
25.8030109393 + 1.357027448 + 0.9253511536 = 28.0853895409
That rounds to about 28.085
Then look at the periodic table to see the atomic mass of Cobalt (Co), Aluminum (Al), Nickel (Ni) and Silicon (Si). The mass values listed in the periodic table are weighted averages of all the isotopes. The units for the mass are still in amu.
- Cobalt = 58.933
- Aluminum = 26.982
- Nickel = 58.693
- Silicon = 28.085
We have a match with silicon, showing that <u>choice D</u> is the final answer.
The two reason behind the invalidity of flame test are false positive and false negative.
while performing the flame test you must have to be accurate otherwise you will get false results may be positive for some element or may be negative in case the element is present. The main reason to get the false positive and false negative is the presence and contamination of sodium.
Answer:
[H2]eq = 0.0129 M
[F2]eq = 1.0129 M
[HF]eq = 0.9871 M
Explanation:
∴ Ke = [HF]² / [H2]*[F2] = 1.15 E2
experiment:
∴ n H2 = 3.00 mol
∴ n F2 = 6.00 mol
∴ V sln = 3.00 L
⇒ [H2]i = 3.00 mol / 3.00 L = 1 M
⇒ [F2]i = 6.00 mol / 3.00 L = 2 M
[ ]i change [ ]eq
H2 1 1 - x 1 - x
F2 2 2 - x 2 - x
HF - x x
⇒ K = (x)² / (1 - x)*(2 - x) = 1.15 E2
⇒ x² / (2 - 3x + x²) = 1.15 E2 = 115
⇒ x² = (2 - 3x + x²)(115)
⇒ x² = 230 - 345x + 115x²
⇒ 0 = 230 - 345x + 114x²
⇒ x = 0.9871
equilibrium:
⇒ [H2] = 1 - x = 1 - 0.9871 = 0.0129 M
⇒ [F2] = 2 - x = 2 - 0.9871 = 1.0129 M
⇒ [HF] = x = 0.9871 M
If you melt and cool silicon dioxide under very special conditions
<span>in the laboratory we can grow a single </span>crystalline<span> form of </span>
<span>silicon dioxide that we call quartz. In quartz crystals all of </span>
<span>the molecules are aligned and bonded together in a regular three </span>
<span>dimensional tetrahedral structure forming a very hard, transparent </span>
<span>material with special electronic properties. </span>
Answer:
H₂(g) + Cl₂(g) → 2HCl(g) + 185kJ
Explanation:
In a chemical reaction, enthalpy of reaction ΔH is a thermodynamic constant that gives information if the reaction is exothermic (Produce heat if reacts) or endothermic (Consume heat if reacts).
In the reaction:
H₂(g) + Cl₂(g) → 2HCl(g) ΔH = -185kJ
As ΔH <0, the reaction is exothermic, that means, <em>produce heat</em>, writing a balanced thermochemical equation:
<em>H₂(g) + Cl₂(g) → 2HCl(g) + 185kJ</em>
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The enthalpy is as a product beacause an exothermic reaction produces heat.
I hope it helps!
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