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3 years ago

Which of the following are indicators of a chemical change?

Chemistry

1 answer:

Ket [755]3 years ago

4 0

Answer:

All unexpected changes: color change (two clear liquids make purple), temperature change, Odor change or formation, precipitate formation (solid forms), and the production of gas.

Explanation:

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How many half-lives are required for the concentration of reactant to decrease to 1.56% of its original value?4247.56.56

neonofarm [45]

Answer:

6 half-lives are required for the concentration of reactant to decrease to 1.56% of its original value.

Explanation:

Using integrated rate law for first order kinetics as:

$[A_t]=[A_0]e^{-kt}$

Where,

$[A_t]$ is the concentration at time t

$[A_0]$ is the initial concentration

Given:

Concentration is decreased to 1.56 % which means that 0.0156 of $[A_0]$ is decomposed. So,

$\frac {[A_t]}{[A_0]}$ = 0.0156

Thus,

$\frac {[A_t]}{[A_0]}=e^{-k\times t}$

$0.0156=e^{-k\times t}$

kt = 4.1604

The expression for the half life is:-

Half life = 15.0 hours

$t_{1/2}=\frac {ln\ 2}{k}$

Where, k is rate constant

So,

$k=\frac {ln\ 2}{t_{1/2}}$

$\frac{4.1604}{t}=\frac {ln\ 2}{t_{1/2}}$

$t = 6\times t_{1/2}$

<u>6 half-lives are required for the concentration of reactant to decrease to 1.56% of its original value.</u>

6 0

3 years ago

Has anyone ever done this atom escape room thing

SVEN [57.7K]

Answer:

1. negative

2. positive

3. neutral

Explanation:

Ok so it looks like they are asking for the charge (positive, negative, or neutral) of each thing

So for 1, it would be negative, because it's pointing to an electron. Electrons always have a negative charge.

So for 2, it would be positive, because it's pointing to a proton. Protons always have a positive charge

So for 3, it would be neutral, because it's pointing to a neutron. Neutrons always have a neutral charge.

4 0

3 years ago

Which element is most likely to gain an electron?

Oduvanchick [21]

B. Fluorine (F) is the right answer

3 0

3 years ago

Matter that is the same throughout is called what

Stolb23 [73]

The matter that has the same composition and properties throughout is called pure chemical substance. So the answer is substance.

6 0

3 years ago

Why are lightning formed in clouds?

VladimirAG [237]

Explanation:

Because opposites attract, the negative charge at the bottom of the storm cloud wants to link up with the ground’s positive charge. Once the negative charge at the bottom of the cloud gets large enough, a flow of negative charge called a stepped leader rushes toward the Earth. The positive charges at the ground are attracted to the stepped leader, so positive charge flows upward from the ground. When the stepped leader and the positive charge meet, a strong electric current carries positive charge up into the cloud. This electric current is known as the return stroke. We see it as the bright flash of a lightning bolt.

Thunder and lightning occur at roughly the same time although you see the flash of lightning before you hear the thunder. This is because light travels much faster than sound

3 0

2 years ago