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just olya [345]
3 years ago
6

Which of the following is a compound? a. iron b. lead c. helium d. methane

Chemistry
1 answer:
Lana71 [14]3 years ago
6 0
The correct answer is d) methane (CH_4)

The other options are elements.
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The small bags of silica gel you often see in a new shoe box are placed there to control humidity. Despite its name, silica gel
Zinaida [17]

So we look equation for the free Gibbs free energy (ΔG) which depends on entalpy (ΔH), temperature (T) and entropy (ΔS):

ΔG = ΔH - TΔS

ΔG is negative (-) because the water absorption on the silica gel surface is a spontaneous process.

ΔH is negative (-) because the water absorption on the silica gel surface is a exothermic process (it releases heat and if you want to desorb the water form the silica gen you need to add heat which is a endothermic process).

ΔS is negative (-) because the water is adsorbed, so from disorderly state you take the water molecules and put them in a orderly state and by doing that you decrease the entropy.

6 0
3 years ago
A sample of a compound of xenon and fluorine contains molecules of a single type; XeFn, where n is a whole number. If 5.0 x 1020
kicyunya [14]

Answer:

4

Explanation:

Avogadro’s number represent the number of the constituent particles which are present in one mole of the substance. It is named after scientist Amedeo Avogadro and is denoted by N_0.

Also, it is the number of particles in exactly 12.000 g of isotope carbon 12.

Avogadro constant:-

N_a=6.023\times 10^{23}

Hence,

Mass of XeF_n = 131.293+ n18.998 g

So,

6.023\times 10^{23}  molecules have a mass of 131.293+ n18.998 g

Also,

1  molecules have a mass of \frac{(131.293+ n18.998)}{6.023\times 10^{23}} g

So,

5.0\times 10^{20}  molecules have a mass of \frac{(131.293+ n18.998)}{6.023\times 10^{23}}\times 5.0\times 10^{20} g

Also, given mass = 0.172 g

Thus,

\frac{(131.293+ n18.998)}{6.023\times 10^{23}}\times 5.0\times 10^{20}=0.172

\frac{18.998n+131.293}{1204.6}=0.172

18.998n+131.293=207.1912

n=\frac{75.8982}{18.998}=4

<u>Thus, value of n is 4.</u>

4 0
3 years ago
Name three elements that are named after people.
natali 33 [55]

Answer:

Bohrium (Niels Bohr)

Curium (Marie and Pierre Curie)

Einsteinium (Albert Einstein

4 0
2 years ago
Read 2 more answers
Copper has average atomic mass of 63.546 amu. It's two isotopes are Cu-63 (which is 69.17% abundant and has a mass of 62.9296 am
garri49 [273]

Answer: 69.152% → 63^Cu

30.848% → 65^Cu

Explanation:

As you know, the average atomic mass of an element is determined by taking the weighted average of the atomic masses of its naturally occurring isotopes.

Simply put, an element's naturally occurring isotopes will contribute to the average atomic mass of the element proportionally to their abundance.

Explanation:

6 0
3 years ago
You are a chemist working in your laboratory. In your storage closet you have a
Nastasia [14]
Ans is B.Bromine. Only two elements are liquid at room temperature ( mercury and Bromine) . Helium and chlorine, arsenic are gases.
8 0
3 years ago
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