Which of the following does NOT contain 3.0 x 1024 atoms?
A.
60 g of carbon
B.
two moles of water
C.
one mole of methane
D.
160 g of sulfur
he formula mass of a compound XClO3 is 106.5. The atomic mass (rounded to the nearest whole number) of X is __________ which is __________.
A.
7, Li
B.
1, H
C.
39, K
D.
23, Na
The formula mass of a compound Ca(MO3)2 is 160. The atomic mass of M is __________ which is __________.
A.
32, S
B.
35, Cl
C.
14, N
D.
12, C
The number of moles of hydrogen gas present in a 1,500 mL container at 298 K and 2 atm pressure is __________.
A.
0.52
B.
0.26
C.
0.12
D.
0.65
A gas under an initial pressure of 0.80 atm is allowed to expand at constant temperature from 2.7 L to 4.5 L. The final pressure becomes __________.
A.
15.2 atm
B.
1.33 atm
C.
12.2 atm
D.
0.48 atm
A gas occupies 340 mL at 273 K and 610 torr. What final temperature would be required to increase the pressure to 1 atm, the volume being held constant?
A.
613°C
B.
340°C
C.
267°C
D.
67°C
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CHEM HELP??? 6 multiple choice questions?
2018-03-10 11:04 pm
回答 (2)
2018-03-11 12:09 am
✔ 最佳答案
1.Avogadro constant = 6.0 × 10²³ /mol
A.
No. of moles of C = (60 g) / (12 g/mol) = 5 mol
No. of moles of C atoms = (5 mol) × (6.0 × 10²³ atoms/mol) = 3.0 × 10²⁴ atoms
B.
Each mole of H₂O contains 3 moles of atoms (2 moles of H atoms and 1 mole of O atoms).
No. of moles of atoms = (2 mol) × 3 = 6 mol
No. of atoms = (6 mol) × (6.0 × 10²³ atoms/mol) = 3.6 × 10²⁴ atoms ≠ 3.0 × 10²⁴ atoms
C.
Each mole of CH₄ contains 5 moles of atoms (1 mole of C atoms and 4 moles of H atoms).
No. of moles of atoms = (1 mol) × 5 = 5 mol
No. of atoms = (5 mol) × (6.0 × 10²³ atoms/mol) = 3.0 × 10²⁴ atoms
D.
No. of moles of S = (160 g) / (32 g/mol) = 5 mol
No. of atoms = (5 mol) × (6.0 × 10²³ atoms/mol) = 3.0 × 10²⁴ atoms
The answer: B. two moles of water
====
2.
Formula mass of XClO₃ = 106.5
(Atomic mass of X) + 35.5 + 16×3 = 106.5
Atomic mass of X = 23,. and thus X is Na
The answer: D. 23, Na
====
3.
Formula mass of Ca(MO₃)₂ = 160
40 + (Atomic mass of M)×2 + 16×6 = 160
Atomic mass of M = 12, and thus M is C
The answer: D. 12, C
====
4.
PV = nRT
No. of moles, n = PV/(RT) = 2 × (1500/1000) / (0.08206 × 298) mol = 0.12 mol
The answer: C. 0.12
====
5.
For a fixed amount of gas under constant temperature: P₁V₁ = P₂V₂
Final pressure, P₂ = P₁ × (V₁/V₂) = (0.80 atm) × (2.7/4.5) = 0.48 atm
The answer: D. 0.48 atm
====
6.
For a fixed amount of gas under constant volume: V₁/T₁ = V₂/T₂
Final temperature, T₂ = T₁ × (V₂/V₁) = (273 K) × (760/610) = 340 K = 67°C
The answer: D. 67°C
2018-03-10 11:23 pm
3.0 x 1024 = 3072
that is a tiny number of atoms. Answer: None of these.
one per customer
that is a tiny number of atoms. Answer: None of these.
one per customer
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