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4 years ago

Can someone help me please??

Chemistry

1 answer:

Xelga [282]4 years ago

4 0

41) Answer is: the average atomic mass of chromium is 52.056.

Ar(⁵⁰Cr) = 50.

ω(⁵⁰Cr) = 4.34% ÷ 100%.

ω(⁵⁰Cr) = 0.0434; relative abundance of chromium-50.

Average mass can calculate by summary of percentege of each isotope.

Ar(Cr) = Ar(⁵⁰Cr) · ω(⁵⁰Cr) + Ar(⁵²Cr) · ω(⁵²Cr) + Ar(⁵³Cr) · ω(⁵³Cr) + Ar(⁵⁴Cr) · ω(⁵⁴Cr).

Ar(Cr)= 50 · 0.0434 + 52 · 0.8379 + 53 · 0.095 + 54 · 0.0237.

Ar(Cr) = 2.17 + 43.571 + 5.035 + 1.280

Ar(Cr) = 52.056.

42) Chlorine has atomic number 17, it means it has 17 protons and 17 electrons.

Electron configuration of chlorine atom: ₁₇Cl 1s² 2s² 2p⁶ 3s² 3p⁵.

Chloride is negative ion of chlorine. Chloride is formed when chlorine gain one lectron.

Chloride anion has 17 protons and 18 electrons (like argon-noble gas).

The electron configuration for the chloride ion: ₁₇Cl⁻ 1s²2s²2p⁶3s²3p⁶.

43) Anwser is: the percent by mass of hydrogen in aspirin is 4.48%.

% calculate by atomic mass of element multiply number of that element in molecule divided by molecular mass of molecule.

Ar(H) = 1.008; the relative atomic mass of hydrogen atom.

Mr(C₉H₈O₄) = 9 · Ar(C) + 8 · Ar(H) + 4 · Ar(O).

Mr(C₉H₈O₄) = 180.157.

ω(H)= 8 · Ar(H) ÷ Mr(C₉H₈O₄) · 100%.

ω(H) = 8 · 1.008 ÷ 180.157 · 100%.

ω(H) = 4.48 %.

44) Balanced chemical reaction:

Cd(NO₃)₂ + 2NH₄Cl → CdCl₂ + 2NH₄NO₃.

This chemical reaction is double displacement reaction - cations (Cd²⁺ and NH₄⁺) and anions (NO₃⁻ and Cl⁻) of the two reactants switch places and form two new compounds.

Cd(NO₃)₂ is cadmium nitrate.

NH₄Cl is amonium chloride.

CdCl₂ is cadmium chloride.

NH₄NO₃ is ammonium nitrate.

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The density of h2 gas in a rigid container is 0.135 g/l at a given temperature. what is the pressure of hydrogen in the flask if

Roman55 [17]

Let's assume that H₂ gas has ideal gas behavior.

Then we can use ideal gas formula,
PV = nRT

Where,
P = Pressure of the gas (Pa)
V = Volume of the gas (m³)
n = moles of the gas (mol)
R = Universal gas constant (8.314 J K⁻¹ mol⁻¹)
T = Temperature in Kelvin (K)

But,
n = m/M,
Where m is mass of the gas (kg) and M is molar mass of the gas (kg/mol)

Hence PV= mTR / M
P = mTR / VM = (m/V)TR / M

m/V = d (density (kg/m³)

By rearranging,
P = dRT / M

d = 0.135 g/L = 0.135 kg/m³
T = (273 + 201) K = 474 K
M = 2 g/mol = 2 x 10⁻³ kg/mol

From substitution,
P = 0.135 kg/m³ x 8.314 J K⁻¹ mol⁻¹ x 474 K / 2 x 10⁻³ kg/mol
P = 266006.43 Pa
P = 266 kPa

Hence the pressure of H₂ gas at 201⁰C is 266 kPa

8 0

4 years ago

2. A convergent boundary is

wel

Answer:

A. When two boundary plates are moving slowly toward each other.

3 0

3 years ago

Which pair of compounds has the same empirical formula? c3h8 and c3h c2h2 and c2h c4h10 and c6h c4h10 and c2h5.

BartSMP [9]

Answer:

The correct answer is the final pair: C4H10 and C2H5

Explanation:

Took the test and it was right. :)

8 0

3 years ago

Vanillin, c8h8o3 (m = 152 g/mol), is the molecule responsible for the vanilla flavor in food. how many oxygen atoms are present

Flauer [41]

Molecular weight of vanillin = 152 g/mol

Futher molecular formula of vanillin is C8H8O3

Atomic weight of oxygen = 16 g/mol

Thus, 152 g of vanillin contains 16 g of oxygen
∴ 0.045 g (45 mg) of vanillin contains $\frac{16X0.045}{152}$ = 0.00473 g

Also, number of moles of vanillin in 0.045 g sample = $\frac{weight}{molecular.weight} = \frac{0.045}{152} = 2.96X10^{-4}$
Now, 1 mole = 6.023 X 10^23 molecules
∴ 2.96 X 10^-4 mole = 1.78 X 10^20 molecules

From molecular formula, it can be seen that 1 molecule of vanallin contain 3 atoms of oxygen
∴1.78 X 10^20 molecules contain 3 X 1.78 X 10^20 = 5.34 X 10^20 oxygen atoms

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4 years ago

If CO2 and NH3 are allowed to effuse through a porous membrane under identical conditions, the rate of effusion for NH3 will be

vladimir1956 [14]

Answer:

1.608

Explanation:

According to Graham's effusion law, the rate of effusion (r) of a gas in inversely proportional to the root square of its molar mass (M). The ratio rNH₃ to rCO₂ is:

$\frac{r_{NH_{3}}}{r_{CO_{2}}} =\sqrt{\frac{M(CO_{2})}{M(NH_{3})}} =\sqrt{\frac{44.01g/mol}{17.03g/mol} } =1.608$

If CO₂ and NH₃ are allowed to effuse through a porous membrane under identical conditions, the rate of effusion for NH₃ will be 1.608 times that of CO₂.

8 0

4 years ago