Pls help asap !!!!!!!!!!!!

Chemistry

1 answer:

Arte-miy333 [17]3 years ago

4 0

Answer:

1st option is correct.............

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melting, boiling, and bending are considered physical changes, but burning is a chemical change. explain why this is so.

Naya [18.7K]

So, when you make something boiling or melting, its still the same substance. Water doesn't change into something else, just change its state of matter. When you burn something, one substance reacts with another. For example, when you burn carbon in oxygen, you get carbon dioxide. That's the difference.

8 0

4 years ago

The half-life of radioactive substance is 2.5 minutes. what fraction of the origional radioactive remains after 10 mins

saul85 [17]

The answer is 1/16.

Half-life is the time required for the amount of a sample to half its value.
To calculate this, we will use the following formulas:
1. $(1/2)^{n} = x$ ,
where:
n - a number of half-lives
x - a remained fraction of a sample

2. $t_{1/2} = \frac{t}{n}$
where:
 $t_{1/2}$ - half-life
t - total time elapsed
n - a number of half-lives

So, we know:
t = 10 min
 $t_{1/2}$ = 2.5 min

We need:
n = ?
x = ?

We could first use the second equation to calculate n:
If:
$t_{1/2} = \frac{t}{n}$ ,
Then:
$n = \frac{t}{ t_{1/2} }$
⇒ $n = \frac{10 min}{2.5 min}$
⇒ $n=4$ 

Now we can use the first equation to calculate the remained fraction of the sample.
 $(1/2)^{n} = x$
⇒ $x=(1/2)^4$
⇒ $x= \frac{1}{16}$

3 0

3 years ago

If an atom has 6 electrons outside of its nucleus, which combination of protons and neutrons would result in a neutral atom?

777dan777 [17]

The answer will be: 6 protons, 6 neutrons.

7 0

4 years ago

Rusting of nail are chemical change or physical change and say why

Svetach [21]

Answer:

Explanation:

‘it’s a chemical change because this may seem like a decomposition reaction because it seems like the nail is decomposing and falling apart.

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3 years ago

Read 2 more answers

You are performing a titration by adding a Strong Base to a solution of Weak Acid. At the equivalence point, will your solution

Alchen [17]

Answer:

Basic

Explanation:

The titration of a strong base with a weak acid would always result in a solution whose pH is greater than 7,i.e a basic solution. For this reason its advisable to use an indicator whose color change will occur in that pH range.

For other cases, the titration of a stong acid and strong will result in a neutral solution and the titration of a weak base versus a strong acid would result in an acidic solution.

3 0

3 years ago