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3 years ago

A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast were they running ?

1 answer:

3 0

Hi Alex, thanks for asking a question here on Brainly!

We can figure how the fast the person is running by dividing the minutes by the seconds.

$\frac{5m}{sec}$
= $\frac{300m}{min}$
= $\frac{18km}{hr}$

The person was running 18 km/hr. ✅

Hope that helps! ★ If you have further questions about this question or need more help, feel free to comment below or post another question and send the link to me. -UnicornFudge aka Nadia.

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Consider the following balanced equation:

Serga [27]

Zn⁰ + 2H⁺ ------> Zn²⁺ + H2⁰

H⁺ ion has oxidation number +1.
Zn²⁺ ion has oxidation number +2.
Atom of Zn has electric charge 0, and each hydrogen atom in the molecule H2 have oxidation number 0. So, Zn and each hydrogen atom in H2 have oxidation numbers equals "0".

Answer is
D. Zn and each hydrogen atom in H2

4 0

3 years ago

How may a substance be tested to determine whether or not it is an element

yaroslaw [1]

Always remember that a compound can be separated into simpler substances by chemical methods/reactions. While elements cannot be broken down into simpler substances by chemical reactions. You can do a flame test and spectrum analysis to determine whether a solid material is an element or a compound. Check the boiling and/or melting point, color or density. Also check the solid material’s reaction with oxygen, hydrogen, calcium, or various acids. Examine and study its physical chemistry. The element(s) that may be present may be identified by checking the absorption edges from an x-ray spectrum.

7 0

3 years ago

Three isotopes of argon occur in nature – 36 18Ar, 38 18Ar, 40 18Ar. Calculate the average atomic mass of argon to two decimal p

likoan [24]

Answer: 3) 39.96 amu

Explanation:

Mass of isotope Ar- 36 = 35.97 amu

% abundance of isotope Ar- 36= 0.337% = $\frac{0.337}{100}=3.37\times 10^{-3}$

Mass of isotope Ar- 38 = 37.96 amu

% abundance of isotope 2 = 0.063 % = $\frac{0.063}{100}=6.3\times 10^{-4}$

Mass of isotope Ar- 40 = 39.96 amu

% abundance of isotope 2 = 99.600 % = $\frac{99.600}{100}=0.996$

Formula used for average atomic mass of an element :

$\text{ Average atomic mass of an element}=\sum(\text{atomic mass of an isotopes}\times {{\text { fractional abundance}})$

$A=\sum[(35.97\times 3.37\times 10^{-3})+(37.96\times 6.3\times 10^{-4})+(39.96\times 0.996)]$

$A=39.96amu$

Therefore, the average atomic mass of argon is 39.96 amu

4 0

3 years ago

How many atoms does the compound 2Zn(OH)2 have? 2 at the end is subscript.

labwork [276]

10 atoms in total
4 atoms of H
4 atoms of O
2 atoms of Zn
Hope this helps :)

7 0

3 years ago

What have six valence electrons

irina1246 [14]

Any element in group 18 has eight valence electrons (except for helium, which has a total of just two electrons). Examples include neon (Ne), argon (Ar), and krypton (Kr). Oxygen, like all the other elements in group 16, has six valence electrons.

6 0

3 years ago

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