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Varvara68 [4.7K]
2 years ago
12

3. A student mixes a solid powder into a beaker of fluid. Which of the following would indicate that a chemical change has defin

itely occurred?​
Chemistry
1 answer:
Ket [755]2 years ago
5 0

Explanation:

A chemical change is a change in which a new kind of substance is produced. Such changes are always accompanied by energy changes.

They are mostly reversible.

Some examples of such reactions are combustion, rusting of iron, precipitation, rancidity of butter, souring of milk.

  • There might be some little change in mass
  • It requires a considerable amount of energy
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makkiz [27]
A forest would have have the most fertile soil
8 0
2 years ago
naturally occurring bromine molecules, br2 have masses of 158, 160, and 162. they occur in the relative abundances 25.69%, 49.99
4vir4ik [10]
The average atomic mass of an element can be determined by multiplying the individual masses of the isotopes with their respective relative abundances, and adding them. 

Average atomic mass of Br = 158 amu(0.2569) + 160 amu(0.4999) + 162 amu(0.2431)
Average atomic mass = 159.96 amu

As described in the problem, the relative abundance for Br-79 is 25.69%. This is because 2 atoms of Br is equal to 79*2 = 158 amu. Similarly, the relative abundance of Br-81 is 81*2 = 162, which is 24.31%.
4 0
3 years ago
An ambulance took 2 hours to cover a distance of 10 kilometers. Find its speed.​
bekas [8.4K]

Answer:

5km/hour

Explanation:

2hours = 10km

/2              /2

1 hour = 5km

7 0
2 years ago
Read 2 more answers
The pH of a 0.150 molar solution of a weak acid is 4.10. What is the pKa of the acid?
Kamila [148]
Answer: 4.21×10⁻⁸

Explanation:


1) Assume a general equation for the ionization of the weak acid:

Let HA be the weak acid, then the ionization equation is:

HA ⇄ H⁺ + A⁻

2) Then, the expression for the ionization constant is:

Ka = [H⁺][A⁻] / [HA]

There, [H⁺] = [A⁻], and [HA] = 0.150 M (data given)


3) So, you need to determine [H⁺] which you do from the pH.

By definition, pH = - log [H⁺]

And from the data given pH = 4.1


⇒ 4.10 = - log [H⁺] ⇒ [H⁺] = antilog (- 4.10) = 7.94×10⁻⁵

4) Now you have all the values to calculate the expression for Ka:

ka = 7.94×10⁻⁵ × 7.94×10⁻⁵ / 0.150 = 4.21×10⁻⁸
3 0
3 years ago
Read 2 more answers
Three Chemistry students find a bottle of colorless liquid in the laboratory and each makes a different suggestions about the id
astra-53 [7]

Answer:

and the question is?

Explanation:

3 0
2 years ago
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