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3 years ago

The rate constant k for a certain reaction is measured at two different temperatures:

Chemistry

1 answer:

bogdanovich [222]3 years ago

8 0

Answer:

Ea=5.5 Kcal/mole

Explanation:

Let rate constant are $K_1$ and $K_2$ at temperature $T_1$ and $T_2$

By using Arrhenius equation at two different two different temperature,

$Log K_1/K_2 =E_a/2.303R*(1/T_2 -1/T_2 );T_1=273+376=649K ;K_1=4.8*10^8;T_2=273+280=553K ;K_2=2.3*10^8;R=2 cal/(mole.K);Log (4.8*10^8)/(2.3*10^8 )=E_a/2.303R*(1/553K-1/649); Log 4.8/2.3=E_a/2.303R*96/358897 ;0.32=E_a/2.303R*96/358897;E_a=(0.32*2.303R*358897)/96;$

By putting value of R=2 cal/mole.K

$E_a=5510.265cal/mole;$

By rounding off upto 2 significant figure;

$E_a=5.5Kcal/mole;$

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Determine the pH of the following base solutions. (Assume that all solutions are at 25°C and the ion-product constant of water,

alexira [117]

Answer:

a) The pH of the solution is 12.13.

b) The pH of the solution is 12.17.

Explanation:

Ionic product of water = $K_w=1.01\times 10^-{14}$

$K_w=[H^+][OH^-]$

$1.01\times 10^-{14}=[H^+][OH^-]$

Taking negative logarithm on both sides:

$-\log[1.01\times 10^-{14}]=(-\log [H^+])+(-\log [OH^-])$

The pH is the negative logarithm of hydrogen ion concentration in solution.

The pOH is the negative logarithm of hydroxide ion concentration in solution.

$13.99=pH+pOH$

a) $1.39\times 10^{-2} M$ of NaOH.

Concentration of hydroxide ions:

$NaOH(aq)\rightarrow Na^+(aq)+OH^-(aq)$

So, $[OH^-]=1\times [NaOH]=1\times 1.39\times 10^{-2} M=1.39\times 10^{-2} M$

$pOH=-\log[1.39\times 10^{-2} M]=1.86$

$13.99=pH+pOH$

$13.99=pH+1.86$

pH=13.99-1.86=12.13

b) $0.0051 M$ of NaOH.

Concentration of hydroxide ions:

$Al(OH)_3(aq)\rightarrow Al^{3+}(aq)+3OH^-(aq)$

So, $[OH^-]=3\times [Al(OH)_3]=3\times 0.0051 M=0.0153 M$

$pOH=-\log[0.0153 M]=1.82$

$13.99=pH+pOH$

$13.99=pH+1.82$

pH=13.99-1.82=12.17

6 0

3 years ago

8. What is the mass of 4.50 x 1022 Cu atoms?

vladimir2022 [97]

Answer:

4.7485 g

Explanation:

4.50 x 10^22 Cu atoms * (1 mol Cu / 6.022 x 10^23 Cu atoms) * 63.546 g Cu/(mol Cu) = 4.7485 g

In every mole of Cu, there are 6.022 x 10^23 atoms (Avogadro's number). The molecular weight of copper is 63.546 g/mol.

5 0

3 years ago

When ethanol is burned, it's converted into carbon dioxide and water. Does the ethanol undergo a physical change or a chemical c

NARA [144]

It's a chemical change because ethanol is converted into other substances.

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3 years ago

The mass percent of oxygen in CaO is what

TEA [102]

Add the reltive atomic mass of Ca and O which are 40 and 16 respectively after addition we get molecular mass of CaO which is 40+16=56 now divide atomic mass of O by molecular mass of CaO and multiply it with 100 as show n 16/56 *100=28.57%

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3 years ago

1. Fred is walking at 1.7 m/s, he sees a dollar and runs at 2.5 m/s in 1.5 seconds.

Firdavs [7]

Answer:

Acceleration is the rate of change of velocity. Usually, acceleration means the speed is changing, but not always. When an object moves in a circular path at a constant speed, it is still accelerating, because the direction of its velocity is changing.

Explanation:

It goes with velocity

5 0

3 years ago