How to calculate the number of moles

if a 2.0g sample of water at 5.0celcius absorbs 21.8Joules of energy, the temprature of the sample will be raised by

Cerrena [4.2K]

You'd use the temperature change equation. The specific heat of water is always 4.18J/(g °C).
Equation to use: q=mCΔT

21.8=(2.0)(4.18)(Tf-5)
21.8=(8.36)(Tf-5)
21.8/8.36=Tf-5
2.61=Tf-5
2.61+5=Tf
Tf=7.61 °C

Since you want to know how many °C it raises, you wouldn't pay attention to the last 2 steps, however if you need to know the final temp, you want to go to the last step.

8 0

3 years ago

[02.06]When electrons are in an unstable state, they will quickly return to their lower energy level. When this happens, energy

inn [45]

The lowest energy state an atom can be at is called its ground state. When an electron in an atom has absorbed energy it is said to be in an excited state. An excited atom is unstable and tends to rearrange itself to return to its lowest energy state. When this happens, the electrons lose some or all of the excess energy by emitting light. Light is only emitted at certain frequencies, each corresponding to a particular electronic transition within the allowed states.

electrons emitting light so the electrons will be in ground state

5 0

3 years ago

Read 2 more answers

Air is compressed from an inlet condition of 100 kPa, 300 K to an exit pressure of 1000 kPa by an internally reversible compress

ElenaW [278]

Answer:

(a) $W_{isoentropic}=8.125\frac{kJ}{mol}$

(b) $W_{polytropic}=7.579\frac{kJ}{mol}$

(c) $W_{isothermal}=5.743\frac{kJ}{mol}$

Explanation:

Hello,

(a) In this case, since entropy remains unchanged, the constant $k$ should be computed for air as an ideal gas by:

$\frac{R}{Cp_{air}}=1-\frac{1}{k} \\\\\frac{8.314}{29.11} =1-\frac{1}{k}\\$

$0.2856=1-\frac{1}{k}\\\\k=1.4$

Next, we compute the final temperature:

$T_2=T_1(\frac{p_2}{p_1} )^{1-1/k}=300K(\frac{1000kPa}{100kPa} )^{1-1/1.4}=579.21K$

Thus, the work is computed by:

$W_{isoentropic}=\frac{kR(T_2-T_1)}{k-1} =\frac{1.4*8.314\frac{J}{mol*K}(579.21K-300K)}{1.4-1}\\\\W_{isoentropic}=8.125\frac{kJ}{mol}$

(b) In this case, since $n$ is given, we compute the final temperature as well:

$T_2=T_1(\frac{p_2}{p_1} )^{1-1/n}=300K(\frac{1000kPa}{100kPa} )^{1-1/1.3}=510.38K$

And the isentropic work:

$W_{polytropic}=\frac{nR(T_2-T_1)}{n-1} =\frac{1.3*8.314\frac{J}{mol*K}(510.38-300K)}{1.3-1}\\\\W_{polytropic}=7.579\frac{kJ}{mol}$

(c) Finally, for isothermal, final temperature is not required as it could be computed as:

$W_{isothermal}=RTln(\frac{p_2}{p_1} )=8.314\frac{J}{mol*K}*300K*ln(\frac{1000kPa}{100kPa} ) \\\\W_{isothermal}=5.743\frac{kJ}{mol}$

Regards.

8 0

2 years ago

Could ethanol vapor collect in low spots?

Leviafan [203]

Answer:

Yes

Explanation:

Denatured ethanol fuel is a polar solvent, which is soluble in water. A

Polar solvent is a compound with a charge separation in chemical bonds, such as alcohol, most acids, or ammonia. These have affinity with water and will dissolve easily. Denatured fuel ethanol has a flash point of -5 ° F and a vapor density of 1.5, indicating that it is heavier than air.

Consequently, ethanol vapors do not rise, similar to the gasoline vapors they are looking for lower altitudes. The specific gravity of denatured fuel ethanol is 0.79, which indicates that it is lighter than water and has a self-ignition temperature of 709 ° F and a boiling point of 165-175 ° F. Like gasoline, the most denatured fuel, the greatest danger of ethanol as an engine fuel component is its flammability.

It has a wider flammable range than gasoline (LEL is 3% and UEL is 19%).

6 0

2 years ago

Write the balanced equation for the ionization of the weak base pyridine, c5h5n , in water, h2o. Phases are optional.

Lelu [443]

The balanced equation for the ionization of the weak base pyridine,C5H5N in water, H2O

C_5H_5N ( aq.) + H2O ( l) ---------> C5H5NH+ (aq.) + OH- (aq.)

<h3>What is the balanced equation for the ionization?</h3>

Generally, Pyridine is characterized by a ring structure, in this characteristic ring structure N is sp2 hybridized, hence creating a lone pair present on N so s - character is more, as well as lone pair, is present.

Therefore, Considering The following functions of the equation:weak base pyridine,C5H5N in water, H2O

We write the balanced equation for the ionization as

C_5H_5N ( aq.) + H2O ( l) ---------> C5H5NH+ (aq.) + OH- (aq.)