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3 years ago

How much heat is released when 24.8 g of ch4 is burned in excess oxygen gas?

Chemistry

1 answer:

balu736 [363]3 years ago

4 0

The given question is incomplete. The complete question is:

How much heat is produced when 24.8 g of $CH_4$ is burned in excess oxygen gas

Given: $CH _4
+2O_2\rightarrow CO_2+2H_2O$ ΔH= −802 kJ.

Answer: 1243.1 kJ

Explanation:

Heat of combustion is the amount of heat released on complete combustion of 1 mole of substance.

Given :

Amount of heat released on combustion of 1 mole of methane = 802 kJ kJ/mol

According to avogadro's law, 1 mole of every substance occupies 22.4 L at NTP, weighs equal to the molecular mass and contains avogadro's number $6.023\times 10^{23}$ of particles.

1 mole of $CH_4$ weighs = 16 g

Thus we can say:

16 g of $CH_4$ on combustion releases heat = 802 kJ

Thus 24.8 g of $CH_4$ on combustion releases = $\frac{802}{16}\times 24.8=1243.1kJ$

Thus heat released when 24.8 g of methane is burned in excess oxygen gas is 1243.1 kJ

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If a substance has a half life of 58 years and starts with 500 g radioactive, how much remains radioactive after 30 years?

Vilka [71]

Answer:

A = 349 g.

Explanation:

Hello there!

In this case, since the radioactive decay kinetic model is based on the first-order kinetics whose integrated rate law is:

$A=Ao*exp(-kt)$

We can firstly calculate the rate constant given the half-life as shown below:

$k=\frac{ln(2)}{t_{1/2}} =\frac{ln(2)}{58year}=0.012year^{-1}$

Therefore, we can next plug in the rate constant, elapsed time and initial mass of the radioactive to obtain:

$A=500g*exp(-0.012year^{-1} *30year)\\\\A=349g$

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3 years ago

In comparison to an atom of F-19 in the ground state, an atom of C-12 in the ground state has(1) three fewer neutrons

mel-nik [20]

(2) three fewer valence electrons is your answer.

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3 years ago

A penny has a mass of 2.50g and the Moon has a mass of ×7.351022kg, How many moles of pennies have a mass equal to the mass of t

baherus [9]

Answer: 122 moles

Procedure:

1) Convert all the units to the same unit

2) mass of a penny = 2.50 g

3) mass of the Moon = 7.35 * 10^22 kg (I had to arrage your numbers because it was wrong).

=> 7.35 * 10^22 kg * 1000 g / kg = 7.35 * 10^ 25 g.

4) find how many times the mass of a penny is contained in the mass of the Moon.

You have to divide the mass of the Moon by the mass of a penny

7.35 * 10^ 25 g / 2.50 g = 2.94 * 10^25 pennies

That means that 2.94 * 10^ 25 pennies have the mass of the Moon, which you can check by mulitiplying the mass of one penny times the number ob pennies: 2.50 g * 2.94 * 10^25 = 7.35 * 10^25.

5) Convert the number of pennies into mole unit. That is using Avogadros's number: 6.022 * 10^ 23

7.35 * 10^ 25 penny * 1 mol / (6.022 * 10^ 23 penny) = 1.22* 10^ 2 mole = 122 mol.

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8 0

3 years ago

A 53. 5 mL ample of an 5. 4 % (m / v) KBr olution i diluted with water o that the final volume i 205. 0 mL Expre your anwer to t

gogolik [260]

The concentration after dilution is 1.4%.

We are aware that concentration and volume are related to each other by the formula -

$C_{1}$ $V_{1}$ = $C_{2}$ $V_{2}$ , where we have initial concentration and volume on Left Hand Side and final concentration and volume on Right Hand Side.

Keep the values to calculate final concentration.

$C_{2}$ = (53.5 × 5.4)/205.0

Performing multiplication on Right and Side

$C_{2}$ = 288.9/205.0

Performing division on Right Hand Side

$C_{2}$ = 1.4%

Hence, the final concentration is 1.4%.

Learn more about concentration -

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The complete question is -

A 53.5 mL sample of an 5.4 % (m/v) KBr solution is diluted with water so that the final volume is 205.0 mL.

Calculate the final concentration and express your answer to two significant figures and include the appropriate units.

3 0

1 year ago

I don't really understand this worksheet question.

Citrus2011 [14]

25/2 and 96/X
CROSS MULTIPLY.

2x=2,400.
divide by 2.
x=1,200.

you take the GIVEN MASS of an element, and you put it on top, the coefficient is what it’s over. i believe this is right

3 0

3 years ago