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3 years ago

What is the difference between a physical change and chemical change? Please be specific and give examples of each.

Chemistry

1 answer:

AnnZ [28]3 years ago

7 0

Answer:

Explanation:

a physical change is the change of the appearance, and a chemical change is the change of the thing.

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There are four hundred participants in the local Thanksgiving 5K race. If 51% of the participants are female, what is the ratio

Paha777 [63]

Answer:

51:49 is the ratio of female participants to male participants.

Explanation:

Percentage of females in the race = 51 %

Percentage of males in the race = 100% - 51 % = 49%

Total participants in race = 400

Number of women participants = $51% of 400=\frac{51}{100}\times 400=204$

Number of men participants = $49% of 400=\frac{49}{100}\times 400=196$

Ratio of female participants to male participants :

$\frac{204}{196}=\frac{51}{49}=51:49$

5 0

4 years ago

How can radioactivity be used to help find the age of an object ?

gogolik [260]

Hope this answers your question Mariaduong159

Radiometric Dating. It's used to find the dates of ricks and other objects based on what the known decay rate of radioactive isotopes. Different forms of this method can also estimate the age of natural and man-made materials.

8 0

4 years ago

The reaction of NO2 with ozone produces NO3 in a second-order reaction overall.

Brilliant_brown [7]

Answer : The rate of reaction is,

$Rate=4.77\times 10^{-19}M/s$

The appearance of $NO_3$ is, $4.77\times 10^{-19}M/s$

Explanation :

The general rate of reaction is,

$aA+bB\rightarrow cC+dD$

Rate of reaction : It is defined as the change in the concentration of any one of the reactants or products per unit time.

The expression for rate of reaction will be :

$\text{Rate of disappearance of A}=-\frac{1}{a}\frac{d[A]}{dt}$

$\text{Rate of disappearance of B}=-\frac{1}{b}\frac{d[B]}{dt}$

$\text{Rate of formation of C}=+\frac{1}{c}\frac{d[C]}{dt}$

$\text{Rate of formation of D}=+\frac{1}{d}\frac{d[D]}{dt}$

$Rate=-\frac{1}{a}\frac{d[A]}{dt}=-\frac{1}{b}\frac{d[B]}{dt}=+\frac{1}{c}\frac{d[C]}{dt}=+\frac{1}{d}\frac{d[D]}{dt}$

From this we conclude that,

In the rate of reaction, A and B are the reactants and C and D are the products.

a, b, c and d are the stoichiometric coefficient of A, B, C and D respectively.

The negative sign along with the reactant terms is used simply to show that the concentration of the reactant is decreasing and positive sign along with the product terms is used simply to show that the concentration of the product is increasing.

The given rate of reaction is,

$NO_2(g)+O_3(g)\rightarrow NO_3(g)+O_2(g)$

The rate law expression will be:

$Rate=k[NO_2][O_3]$

Given:

Rate constant = $k=1.69\times 10^{-4}M^{-1}s^{-1}$

$[NO_2]$ = $1.77\times 10^{-8}M$

$[O_3]$ = $1.59\times 10^{-7}M$

$Rate=k[NO_2][O_3]$

$Rate=(1.69\times 10^{-4})\times (1.77\times 10^{-8})\times (1.59\times 10^{-7})$

$Rate=4.77\times 10^{-19}M/s$

The expression for rate of appearance of $NO_3$ :

$\text{Rate of reaction}=\text{Rate of appearance of }NO_3=+\frac{d[NO_3]}{dt}$

As, $\text{Rate of reaction}=4.77\times 10^{-19}M/s$

So, $\text{Rate of appearance of }NO_3=+\frac{d[NO_3]}{dt}=4.77\times 10^{-19}M/s$

Thus, the appearance of $NO_3$ is, $4.77\times 10^{-19}M/s$

7 0

3 years ago

PLEASE SOMEONE HELP ME WITH THIIS QUESTION

sdas [7]

Answer:

The correct answer is - 5 carbon compounds due to low to high intermolecular forces between their molecules.

Explanation:

Bottle C has gas in it and we know that alkane has carbon and hydrogen only which means they have a single sigma bond between them and very low intermolecular forces in between molecules and are present mostly at gaseous state. Thus, bottle C has alkane.

Alcohols have -OH group that can form rarely two pi bonds which means they have intermediate intermolecular force whereas acids have -cooH group with a high molecular force so bottle B with liquid is alcohol and A has acid.

3 0

3 years ago

Can someone help me with 3

lozanna [386]

Solidification i believe

5 0

4 years ago