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ki77a [65]
3 years ago
15

What is the mass of 12.3 moles of helium (He)?

Chemistry
1 answer:
anzhelika [568]3 years ago
6 0

Answer : The mass of 12.3 moles of helium (He) is, 49.2 grams.

Solution : Given,

Moles of helium = 12.3 moles

Molar mass of helium = 4 g/mole

Formula used :

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

\text{Mass of helium}=(12.3mole)\times (4g/mole)=49.2g

Therefore, the mass of 12.3 moles of helium (He) is, 49.2 grams.

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A mixture of water and graphite is heated to 600 K in a 1 L container. When the system comes to equilibrium it contains 0.17 mol
Kryger [21]

Answer:

0.44 moles

Explanation:

Given that :

A mixture of water and graphite is heated to 600 K in a 1 L container. When the system comes to equilibrium it contains 0.17 mol of H2, 0.17 mol of CO, 0.74 mol of H2O, and some graphite.

The equilibrium constant K_c=  \dfrac{[CO][H_2]}{[H_2O]}

The equilibrium constant  K_c=  \dfrac{(0.17 )(0.17)}{0.74}

The equilibrium constant K_c=  0.03905

Some O2 is added to the system and a spark is applied so that the H2 reacts completely with the O2.

The equation for the reaction is :

H_2 + \dfrac{1}{2}O_2 \to H_2O \\ \\ 0.17 \ \ \ \ \  \ \ \ \ \to0.17

Total mole of water now = 0.74+0.17

Total mole of water now = 0.91 moles

Again:

K_c=  \dfrac{[CO][H_2]}{[H_2O]}

0.03905 =  \dfrac{[0.17+x][x]}{[0.91 -x]}

0.03905(0.91 -x) = (0.17 +x)(x)

0.0355355 - 0.03905x = 0.17x + x²

0.0355355 +0.13095 x -x²

x² - 0.13095 x - 0.0355355 = 0

By using quadratic formula

x = 0.265  or   x = -0.134

Going by the value with the positive integer; x = 0.265 moles

Total moles of CO in the flask when the system returns to equilibrium is :

= 0.17 + x

= 0.17 + 0.265

= 0.435 moles

=0.44 moles (to two significant figures)

3 0
4 years ago
2O POINTS AND BRAINLIEST!!! FAST ANSWER PLEASE!!!! I WILL FAIL THIS IF YOU DON'T HELP ME!!!!!!
Flauer [41]
 <span>1. 1 molecule of C6H12O6(dextrose sugar), 2 molecles of c2h6o (ethyl alcohol), 2 molecules of Co2 

2. 48 hydrogen atoms </span>
8 0
3 years ago
Read 2 more answers
The half life for the first order conversion of A to B is 56.6 hours. How long does it take for the concentration of A to decrea
sveta [45]

Answer:

It will take 188.06 hours for the concentration of A to decrease 10.0% of its original concentration.

Explanation:

A → B

Initial concentration of the reactant = x

Final concentration of reactant = 10% of x = 0.1 x

Time taken by the sample, t = ?

Formula used :

A=A_o\times e^{-\lambda t}\\\\\lambda =\frac{0.693}{t_{\frac{1}{2}}}

where,

A_o = initial concentration of reactant

A = concentration of reactant left after the time, (t)

t_{\frac{1}{2}} = half life of the first order conversion  = 56.6 hour

\lambda = rate constant

A=A_o\times e^{-(\frac{0.693}{t_{1/2}})\times t}

Now put all the given values in this formula, we get

0.1x=x\times e^{-(\frac{0.693}{56.6 hour})\times t}

t = 188.06 hour

It will take 188.06 hours for the concentration of A to decrease 10.0% of its original concentration.

4 0
3 years ago
Complete this sentence. If mass remains the same while the volume of a substance ________, the density of the substance will____
VARVARA [1.3K]

Answer:

B. Increases, Decreases

Explanation:

I majored in Chemistry

4 0
3 years ago
5 meters
Feliz [49]

Answer:

9

Explanation:

7 0
3 years ago
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