A 32.0 mL sample of hydrogen is collected over water at 20.0°C and 750.0 mm Hg. What is the volume of the dry gas at STP?

Why does a gold isotope, with an atomic number of 79, require more neutrons to be stable than a sodium isotope, with an atomic n

Leya [2.2K]

Here’s a simplified explanation.

The protons in the nucleus repel each other. The neutrons provide the “glue” that holds the nucleus together and prevents it from flying apart.

The “glue” is the strong nuclear force. It is strong but extremely short range. It falls off extremely rapidly as the p-n distance increases.

A neon atom has 10 protons. There are three stable isotopes, with 10, 11, and 12 neutrons.

With fewer than 10 protons, the glue is not strong enough to hold the nucleus together.

If there are more than 12 neutrons, the average p-n distance is great enough that the glue has again become too weak.

Gold has one stable isotope. It contains 79 protons and 118 neutrons.

If there are fewer than 118 neutrons, the proton repulsions will be too strong for the strong force. If there are more than 118 neutrons, the average p-n distance will be large enough that the glue will again be too weak to hold the nucleus toge ther.

8 0

3 years ago

Why is DDT a dangerous environmental pollutant?

oksano4ka [1.4K]

DDT was one of the first chemicals in widespread use as a pesticide.
Food supplies: USDA found DDT breakdown products in 60% of heavy cream samples, 42% of kale greens, 28% of carrots and lower percentages of many other foods.Body burden: DDT breakdown products were found in the blood of 99% of the people tested by CDC.Health impacts: Girls exposed to DDT before puberty are 5 times more likely to develop breast cancer in middle age, according to the President’s Cancer Panel.

5 0

3 years ago

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Which set of data would be best illustrated with a graph bar?

polet [3.4K]

Answer:

Graphs should be titled.

Although the bunnies feed foxes, if there are TOO many foxes, they don’t go well; so that looked cyclic to me. It is a good argument.

STUDY VS GRADES is INCREASINGLY

OBVIOUS! I already know what hummingbirds like. Rain can help wash the smoke from forest fires from the air; do you pick one, OK?

Don’t be nervous - study more. I’ve had a great many students, and they not only survived my classes - most THRIVED!

Explanation:

5 0

3 years ago

Find the pH of the equivalence point and the volume (mL) of 0.0372 M NaOH needed to reach the equivalence point in the titration

elixir [45]

Answer:

8.54

Explanation:

At equivalence point :

42.2 X 0.052 = Vol. NaOH X 0.0372

Vol of NaOH = 2.1944/0.0372 = 58.99 ml

So volume of NaOH recquired to reach equivalence point = 58.99 ml

Number of miliimoles of CH3COOH = molarity X volume in ml = 42.2 X 0.052 = 2.1944 millimoles

Number of millimoles of NaOH = 58.99 X 0.0372 = 2.1944

Now CH₃COOH and NaOH reacts to give CH₃COONa according to the reaction :

CH₃COOH + NaOH ------> CH₃COONa + H₂O

1 mole of CH₃COOH reacts with 1 mole of NaOH to give 1 mole of CH₃COONa

So 2.1944 millimoles of CH₃COOH will react with 2.1944 millimoles of NaOH to give 2.1944 millimoles of CH₃COONa

So all the acid (CH₃COOH) and base (NaOH) has been converted into salt (CH₃COONa) so there is no acid or base left.

Now molarity of CH₃COONa = number of millimoles of CH₃COONa/total volume in ml = 2.1944/(58.99 + 42.2) = 2.1944/101.19 = 0.02169 M

So using the hydrolysis equation :

pH = 1/2 [ pKw + pKa + log c ]

Ka for acetic acid = 1.75 X 10⁻⁵

so pKa = -log (1.75 X 10⁻⁵) = 4.74

Kw = 10⁻¹⁴

so pKw = -log 10⁻¹⁴ = 14

c = 0.02169

so log c = log 0.02169 = -1.66

putting the values....

pH = 1/2 [14 + 4.74 - 1.66 ]

pH = 1/2 [ 17.08] = 8.54

6 0

3 years ago

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Elements within the same group of the periodic table behave similarly because they have the same number of ?

sammy [17]

The elements in each group have the same number of electrons in the outer orbital. Or also called valence electrons. Khan academy has a great video online explaining why this happens. (It only happens for main group elements). Here is a link (sorry you can’t click it in Brainly) https://www.khanacademy.org/science/chemistry/periodic-table/copy-of-periodic-table-of-elements/v/periodic-table-valence-electrons. Feel free to message me for a better explanation, I would explain now but I’m not sure how much you know about this. If you know how to write an electron configuration you can see how all the electron configurations for the same group (not the transitional metals only the main groups) have the same number of valence electrons. I hope that helped, sorry I was vague about the explanation :)

4 0

3 years ago