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3 years ago

Gold is the [...] of a valuable element. A. Chemical formula. B. Symbol. C. Name

Chemistry

2 answers:

Andreyy893 years ago

6 0

The NAME of a valuable element

pychu [463]3 years ago

3 0

Answer:

C. Name

Explanation:

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A volume of 80.0 mL of H2O is initially at room temperature (22.00 ∘C). A chilled steel rod at 2.00 ∘C is placed in the water. I

murzikaleks [220]

Answer:

The mass of the steel bar is 26.833 grams

Explanation:

Step 1: data given

ΣQ gained = ΣQ lost

Q=m*C*ΔT

with m = mass in grams

with C= specific heat capacity ( in J/(g°C))

with ΔT = change in temperature = T2-T1

Qsteel = Qwater

msteel * Csteel * (T2steel - T1steel) = mwater * Cwater * (T2water - T1water)

Mass of steel = TO BE DETERMINED

mass of water =⇒ since 1mL = 1g : 80 mL = 80g

Csteel =0.452 J/(g °C

Cwater = 4.18 J/(g °C

initial temperature steel T1 : 2 °C

final temperature steel T2 = 21.3 °C

initial temperature water T1 =22 °C

final temperature water T2 = 21.3 °C

Step 2: Calculate mass of steel

msteel * Csteel * (T2steel - T1steel) = mwater * Cwater * (T2water - T1water)

msteel * 0.452 *(21.3-2) = 80 * 4.18 * (21.3-22)

msteel = (80 * 4.18 * (-0.7)) / (0.452 * 19.3)

msteel = -234.08 / 8.7236

msteel = -26.833 g

Since mass can't be negative we should take the absolute value of it = 26.833g

The mass of the steel bar is 26.833 grams

6 0

2 years ago

Calculate ∆G ◦ r for the decomposition of mercury(II) oxide 2 HgO(s) → 2 Hg(ℓ) + O2(g) ∆H◦ f −90.83 − − (kJ · mol−1 ) ∆S ◦ m 70.

bagirrra123 [75]

Answer:

4. +117,1 kJ/mol

Explanation:

ΔG of a reaction is:

ΔGr = ΔHr - TΔSr (1)

For the reaction:

2 HgO(s) → 2 Hg(l) + O₂(g)

ΔHr: 2ΔHf Hg(l) + ΔHf O₂(g) - 2ΔHf HgO(s)

As ΔHf of Hg(l) and ΔHf O₂(g) are 0:

ΔHr: - 2ΔHf HgO(s) = 181,66 kJ/mol

In the same way ΔSr is:

ΔSr= 2ΔS° Hg(l) + ΔS° O₂(g) - 2ΔS° HgO(s)

ΔSr= 2* 76,02J/Kmol + 205,14 J/Kmol - 2*70,19 J/Kmol

ΔSr= 216,8 J/Kmol = 0,216 kJ/Kmol

Thus, ΔGr at 298K is:

ΔGr = 181,66 kJ/mol - 298K*0,216kJ/Kmol

ΔGr = +117,3 kJ/mol ≈ 4. +117,1 kJ/mol

I hope it helps!

5 0

3 years ago

Mass of One Water Molecule? The answer says the mass of one water molecule is 2.99 X 10^-23

zmey [24]

The mass of one mole of water it is 18 amu, but you need to find the mass of a molecule of water, therefore you calculate the mass of one mole of water, which is 18 amu and you divided by Avogadro's number which is 6,022 x 10^23. The result is 2,989 x 10^-23. Hope I helped you. If you have any questions ask :) Good luck.

6 0

3 years ago

A buffer is prepared containing 0.75 M NH3 and 0.20 M NH4 . Calculate the pH of the buffer using the Kb for NH3. g

denis-greek [22]

Answer:

pH=8.676

Explanation:

Given:

0.75 M $NH_{3}$

0.20 M $NH_{4}$

The objective is to calculate the pH of the buffer using the kb for $NH_3$

Formula used:

$pOH=pka+log\frac{[salt]}{[base]}\\$

pH=14-pOH

Solution:

On substituting salt=0.75 and base=0.20 in the formula

$pOH=-log(1.77*10^{-5})+log\frac{0.75}{0.20}\\ =4.75+0.5740\\ =5.324$

pH=14-pOH

On substituting the pOH value in the above expression,

pH=14-5.324

Therefore,

pH=8.676

3 0

3 years ago

A sample of carbon-12 has a mass of 6.00 g. How many atoms of carbon-12 are in the sample?

Vesna [10]

Convert grams to moles [grams/molar mass] ~ Moles
Convert moles to atoms [moles * 6.02 x 10^23] = Atoms
Half of 6.02 x 10^23 is 3.01 x 10^23 so here is our answer.

3 0

3 years ago

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