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Nitella [24]
4 years ago
11

What is the mass of 18.8 moles of helium (He) atoms

Chemistry
2 answers:
Aleonysh [2.5K]4 years ago
6 0
Mass = 18.8 g × 4.00/mol = 75.2 g
blsea [12.9K]4 years ago
3 0

Answer : The mass of 18.8 moles of helium atoms are, 75.2 grams

Explanation : Given,

Moles of helium atom = 18.8 moles

Molar mass of helium atom = 4 g/mole

Formula used :

\text{Mass of helium atom}=\text{Moles of helium atom}\times \text{Molar mass of helium atom}

Now put all the given values in this formula, we get the mass of helium atom.

\text{Mass of helium atom}=18.8mole\times 4g/mole

\text{Mass of helium atom}=75.2g

Therefore, the mass of 18.8 moles of helium atoms are, 75.2 grams

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Why does styrofoam fall slower than a rock
mina [271]

Answer:

The foam board has a larger gravitational force but it also has a very large air resistance force. The net (total) force on the foam board will give it a smaller acceleration than paper.

Explanation:

The air molecules get knocked away and take some of the kinetic energy away from the object, which makes the object slow down

4 0
3 years ago
A truck is moving at the rate of 40 km/hr. How far does it move when it stops after 5 seconds?
seraphim [82]
First of all, this is the chemistry section, while your question is a physics question. Anyway I'll tell you how to solve it.

First we need to find the rate that the truck moves in a second.

1km = 1000m
40km = 40000m
40000m/hr
1 hour = 60 minutes
40000m/hr ÷ 60 = 666.66(repeating)/minute
1 minute = 60 seconds
666.66m/min ÷ 60 = 11.11(rep)m/s

Next we simply multiply the speed of the truck by the number of seconds it travels.

11.11 × 5 = 55.55
Make sure to round it unless you indicate the repeating decimal.
The truck moved 55.56m in 5 seconds.
6 0
3 years ago
One of the compounds used to increase the octane rating of gasoline is toluene (pictured). suppose 8.30 ml of toluene (d = 0.867
GrogVix [38]
Missing question:<span> How many grams of oxygen are needed for complete combustion of the toluene?
Chemical reaction: </span>C₇H₈ + 9O₂ → 7CO₂ + 4H₂<span>O.
V(</span>C₇H₈) = 8,30 ml.
d(C₇H₈) = 0,867 g/ml.
n(C₇H₈) = V(C₇H₈) · d(C₇H₈).
m(C₇H₈) = 8,3 ml · 0,867 g/ml.
m(C₇H₈) = 7,19 g.
n(C₇H₈) = m(C₇H₈) ÷ M(C₇H₈).
n(C₇H₈) = 7,19 g ÷ 92,14 g/mol = 0,078 mol.
From chemical reaction: n(C₇H₈) : n(O₂) = 1 : 9.
n(O₂) = 9 · 0,078 mol = 0,702 mol.
m(O₂) = 0,702 mol · 32 g/mol = 22,5 g.
3 0
3 years ago
If the pressure, volume, and the number of moles of a gas are known, which is needed to calculate the universal gas constant fro
umka21 [38]

Answer:

5

Explanation:

7 0
3 years ago
What category of elements does krypton gas belong to?
levacccp [35]
C. Krypton is a noble gas, on the right side of the period table, making it a non-metal.
6 0
4 years ago
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