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Ulleksa [173]
3 years ago
9

What are the four ways to tell if a chemical change has occurred?

Chemistry
1 answer:
Greeley [361]3 years ago
7 0

Answer:

Four ways to tell if a chemical change has occurred is if:

   Production of Gas (Bubble Formation)

   Change in Odor

   Change in Color

   Temperature Change (Is it hotter or colder?)

Explanation:

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You are asked to write observations about a 100g sample of Nitrogen-16 before it decays, but you're running late. In order to ma
san4es73 [151]

Answer:

You cannot make observations if you are 57 seconds late into the lab.

Explanation:

The atomic nucleus can split by decay into 2 or more particles as a result of the instability of its atomic nucleus due to the fact that radioactive elements possess an unstable atomic nucleus.

Now, the primary particles which are emitted by radioactive elements in order to make them decay are alpha, beta & gamma particles.

The half life equation is;

N_t = N₀(½)^(t/t_½)

Where:

t = duration of decay

t_½ = half-life

N₀ = number of radioactive atoms initially

N_t = number of radioactive atoms remaining after decay over time t

We are given;

t = 57 secs

N₀ = 100 g

Now, half life of Nitrogen-16 from online sources is 7.2 seconds. t_½ = 7.2

Thus;

N_t = 100(1/2)^(57/7.2)

N_t = 0.4139g

We are told that In order to make observations, you require at least .5g of material.

The value of N_t you got is less than 0.5g, therefore you cannot make observations if you are 57 seconds late.

5 0
2 years ago
Group 1A (or IA) of the periodic table are the alkali metals: hydrogen (H), lithium (Li), sodium (Na), potassium (K), rubidium (
ziro4ka [17]

Answer: with a non metallic atom

Explanation:

3 0
3 years ago
You dissolve 0.47 g of potassium chloride (KCl) in 700 ml of water.
lana [24]

Answer:

0.009

Explanation:

Molarity, a measure of molar concentration of a substance is calculated thus;

Molarity = number of moles ÷ volume

According to the provided information, mass of KCl = 0.47g, volume of water = 700ml

Using mole = mass/molar mass

Molar Mass of KCl = 39.10 + 35.453

= 74.553g/mol

Mole = 0.47/74.55

Mole = 0.0063mol

Volume of water = 700ml = 700/1000 = 0.7L

Molarity = 0.006/0.7

Molarity = 0.00857

The value of molarity rounded to three decimal places (3 d.p) = 0.009

6 0
3 years ago
Which element forms an ionic compound when it reacts with lithium?
creativ13 [48]
<h3>Answer:</h3>

              Br (Bromine)

<h3>Explanation:</h3>

Li and K,

As the electronegativity difference between Li and K is less than 1.7 therefore, ionic bond cannot form between these two metals.

Li and Fe,

The electronegativity difference is less than 1.7 so neither electron loss nor electron gaining will take place between these two metals. Therefore, there will be no ionic bond between them.

Li and Kr,

As Krypton is a noble gas and does not react due to complete octet hence the formation of KrLi is difficult. However, Krypton can make compounds like KrF₂ e.t.c. Therefore we can skip this option.

For Li and K,

                   E.N of Bromine             =   2.96

                   E.N of Lithium               =   0.98

                                                             ________

                   E.N Difference                     1.98          (Ionic)

This ionic compound is possible and is the correct option because ionic compounds are always made by metals and non metals and here the combination is perfect.

<h3>Conclusion:</h3>

                          Lithium (a metal) and form Ionic bond with Bromine (a non metal)

4 0
3 years ago
Read 2 more answers
What does it mean when we say "kinetic energy in an electron"?
Rufina [12.5K]
Temperature is a statistical quantity. The formal definition<span> is T = dU/dS, the change in internal </span>energy<span> with respect to entropy holding volume and particle number constant. A practical </span>definition<span> comes from the fact that the atoms, molecules, or whatever particles in a system have an </span>average kinetic energy<span>.</span>
7 0
3 years ago
Read 2 more answers
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