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3 years ago

Why are atoms considered the smallest particles of an element?

2 answers:

3 0

Atoms are considered the smallest particles of an element because they are the basic unit. They cannot be broken down into any smaller substance.

Vlada [557]3 years ago

3 0

They are considered the smallest part of an element because when you break down an element into smaller and smaller parts, theoretically when you reach thed smallest part and you cant break it any more, it will be one atom of whatever element you are breaking down.

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What is the pH of .0003 M of NaOH

s344n2d4d5 [400]

We are given that the concentration of NaOH is 0.0003 M and are asked to calculate the pH

We know that NaOH dissociates by the following reaction:

NaOH → Na⁺ + OH⁻

Which means that one mole of NaOH produces one mole of OH⁻ ion, which is what we care about since the pH is affected only by the concentration of H⁺ and OH⁻ ions

Now that we know that one mole of NaOH produces one mole of OH⁻, 0.0003M NaOH will produce 0.0003M OH⁻

Concentration of OH⁻ (also written as [OH⁻]) = 3 * 10⁻⁴

<u>pOH of the solution:</u>

pOH = -log[OH⁻] = -log(3 * 10⁻⁴)

pOH = -0.477 + 4

pOH = 3.523

<u>pH of the solution:</u>

We know that the sum of pH and pOH of a solution is 14

pH + pOH = 14

pH + 3.523 = 14 [subtracting 3.523 from both sides]

pH = 10.477

8 0

3 years ago

The symbol, Mg(s), shows magnesium in its standard state. True or False?

puteri [66]

Answer:

True?

Explanation:

8 0

3 years ago

The gas-phase reaction follows an elementary rate law and is to be carried out first in a PFR and then in a separate experiment

astraxan [27]

Answer:

The activation energy is $=8.1\,kcal\,mol^{-1}$

Explanation:

The gas phase reaction is as follows.

$A \rightarrow B+C$

The rate law of the reaction is as follows.

$-r_{A}=kC_{A}$

The reaction is carried out first in the plug flow reactor with feed as pure reactant.

From the given,

Volume "V" = $10dm^{3}$

Temperature "T" = 300 K

Volumetric flow rate of the reaction $v_{o}=5dm^{3}s$

Conversion of the reaction "X" = 0.8

The rate constant of the reaction can be calculate by the following formua.

$V= \frac{v_{0}}{k}[(1+\epsilon )ln(\frac{1}{1-X}-\epsilon X)]$

Rearrange the formula is as follows.

$k= \frac{v_{0}}{V}[(1+\epsilon )ln(\frac{1}{1-X}-\epsilon X)]............(1)$

The feed has Pure A, mole fraction of A in feed $y_{A_{o}}$ is 1.

$\epsilon =y_{A_{o}}\delta$

$\delta$ = change in total number of moles per mole of A reacte.

$=1(2-1)=1$

Substitute the all given values in equation (1)

$k=\frac{5m^{3}/s}{10dm^{3}}[(1+1)ln \frac{1}{1-0.8}-1 \times 0.8] = 1.2s^{-1}$

Therefore, the rate constant in case of the plug flow reacor at 300K is $1.2s^{-1}$

The rate constant in case of the CSTR can be calculated by using the formula.

$\frac{V}{v_{0}}= \frac{X(1+\epsilon X)}{k(1-X)}.............(2)$

The feed has 50% A and 50% inerts.

Hence, the mole fraction of A in feed $y_{A_{o}}$ is 0.5

$\epsilon =y_{A_{o}}\delta$

$\delta$ = change in total number of moles per mole of A reacted.

$=0.5(2-1)=0.5$

Substitute the all values in formula (2)

$\frac{10dm^{3}}{5dm^{3}}=\frac{0.8(1+0.5(0.8))}{k(1-0.8)}=2.8s^{-1}$

Therefore, the rate constant in case of CSTR comes out to be $2.8s^{-1}$

The activation energy of the reaction can be calculated by using formula

$k(T_{2})=k(T_{1})exp[\frac{E}{R}(\frac{1}{T_{1}}-\frac{1}{T_{2}})]$

In the above reaction rate constant at the two different temperatures.

Rearrange the above formula is as follows.

$E= R \times(\frac{T_{1}T_{2}}{T_{1}-T_{2}})ln\frac{k(T_{2})}{k(T_{1})}$

Substitute the all values.

$=1.987cal/molK(\frac{300K \times320K}{320K \times300K})ln \frac{2.8}{1.2}=8.081 \times10^{3}cal\,mol^{-1}$

$=8.1\,kcal\,mol^{-1}$

Therefore, the activation energy is $=8.1\,kcal\,mol^{-1}$

8 0

3 years ago

Explain how the digestive/excretory system is similar to a recycling center

CaHeK987 [17]

Answer:

The digestive system is a system where our body breaks down food to acquire important nutrients. This is the same as your local recycling center because they collect and breaks the plastic down to be reused into recycled products.

The excretory system is a system where we remove excess unnecessary materials. This can be the same as the recycling center because they remove unnecessary materials (such as trash that is not meant to be recycled).

7 0

2 years ago

Chose all of the correct statements pure vs mixture

GarryVolchara [31]

Answer:

I think that a pure substance is a form of matter that has a constant composition and properties that are constant throughout the sample. Mixtures are physical combinations of two or more elements and/or compounds.

Explanation:

6 0

2 years ago