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3 years ago

Which of these is an indication that a chemical reaction has occurred?

Chemistry

2 answers:

kirill [66]3 years ago

8 0

C. Formation of a precipitate.

Kobotan [32]3 years ago

7 0

Answer:

The correct option is C.
Formation of a precipitate

Explanation:

During a chemical reaction, new substances are formed known as a products, mostly reaction occur and their product is obtained as precipitates.

Example

Arylidene-2-thiobarbituric acid is obtained as precipitates when aldehyde and thiobarbituric acid react to each other.

melting of a substance

It is just indication of physical changes, like melting of ice, composition remained same as before.

boiling of a substance

It is just indication of physical changes, like boiling of water into vapors, composition remained same as before.

freezing of a substance

It is just indication of physical changes, like freezing of water into ice, composition remained same as before

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Will GIVE BRAINLIEST --A student makes a standard solution of potassium hydroxide by adding 14.555 g to 500.0 mL of water. Answe

leva [86]

Answer:

0.5188 M or 0.5188 mol/L

Explanation:

Concentration is calculated as molarity, which is the number of moles per litre.

***Molarity is represented by either "M" or "c" depending on your teacher. I will use "c".

The formula for molarity is:

$c = \frac{n}{V}$

n = moles (unit mol)

V = volume (unit L)

Find the molar mass (M) of potassium hydroxide.

$M_{KOH} = \frac{39.098 g}{mol}+\frac{16.000 g}{mol}+\frac{1.008 g}{mol}$

$M_{KOH} = 56.106 \frac{g}{mol}$

Calculate the moles of potassium hydroxide.

$n_{KOH} = \frac{14.555 g}{1}*\frac{1mol}{56.106g}$

$n_{KOH} = 0.25941(9)mol$

Carry one insignificant figure (shown in brackets).

Convert the volume of water to litres.

$V = \frac{500.0mL}{1}*\frac{1L}{1000mL}$

$V = 0.5000L$

Here, carrying an insignificant figure doesn't change the value.

Calculate the concentration.

$c = \frac{n}{V}$

$c = \frac{0.25941(9)mol}{0.5000 L}$

$c = 0.5188(3) \frac{mol}{L}$ <= Keep an insignificant figure for rounding

$c = 0.5188 \frac{mol}{L}$ <= Rounded up

$c = 0.5188M$ <= You use the unit "M" instead of "mol/L"

The concentration of this standard solution is 0.5188 M.

7 0

3 years ago

Greater than ___________ mcg/dl is considered a high level of morning cortisol.

Natalija [7]

Greater than 23mcg/dl is considered a high level of morning cortisol.

Normally, cortisol levels rise during the early morning hours and are highest about 7AM. They drop very low in the evening and during the early phase of sleep. If you do not have this daily change (diurnal rhythm) in cortisol levels, you may have overactive adrenal glands. This condition is called Cushing's syndrome.

5 0

3 years ago

You unknowingly run over a small nail while driving and it punctures your tire. When you are getting in your car the next mornin

Norma-Jean [14]

The nails can puncture the tires of the vehicles making them deflated after a while. The process of tire deflation due to a puncture is due to the process called an effusion. Thus, option c is correct.

<h3>What is effusion?</h3>

Effusion is the process that defines the escape of the fluids or gases from a system through an outlet with a small diameter compared to the mean free path of the molecules.

When a tire is punctured then the gas from the tire starts to move out through the hole through effusion. This leads to deflation of the tire after some time as all the gas present inside had moved out completely.

Therefore, option c. a punctured tire deflates due to effusion.

Learn more about effusion here:

brainly.com/question/2823560

#SPJ1

7 0

2 years ago

2. The pressure of the oxygen gas inside a

Flauer [41]

Answer: 4.41 atm

Explanation:

Given that,

Original pressure of oxygen gas (P1) = 5.00 atm

Original temperature of oxygen gas (T1) = 25°C

[Convert 25°C to Kelvin by adding 273

25°C + 273 = 298K

New pressure of oxygen gas (P2) = ?

New temperature of oxygen gas (T2) = -10°C

[Convert -10°C to Kelvin by adding 273

-10°C + 273 = 263K

Since pressure and temperature are given while volume is held constant, apply the formula for Charle's law

P1/T1 = P2/T2

5.00 atm /298K = P2/263K

To get the value of P2, cross multiply

5.00 atm x 263K = 298K x V2

1315 atm•K = 298K•V2

V2 = 1315 atm•K / 298K

V2 = 4.41 atm

Thus, the new pressure inside the canister is 4.41 atmosphere

4 0

3 years ago

the combustion of a sample butane, C4H10 (lighter fluid) produced 2.46 grams of water. how many moles of water formed

enyata [817]

$2C_4H_{10}+13O_2$ ⇒ $8CO_2 + 10H_2O$

$n= \frac{m}{M} = \frac{m}{2M(H)+M(O)}= \frac{2,46}{2*1,0+16,0} = 0,14mol$

So 0,14mol are formed.

6 0

3 years ago