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frozen [14]
3 years ago
9

How many protons,neutrons and electrons are present in an atom of hafnium,hf,with a mass number of 178?

Chemistry
2 answers:
AleksAgata [21]3 years ago
7 0
178 of each species
178 protons
178 neutrons
And 178 electrons
AlladinOne [14]3 years ago
4 0

Answer:

72 protons

102 neutrons

72 electrons

Explanation:

Hf has an atomic number of 72. By definition, this means that it has 72 protons.

It also has a mass number of 178. The mass number (A) counts all elements with significant mass (protons and neutrons). Then,

A = p⁺ + n⁰

n⁰ = A - p⁺ = 178 - 72 = 102

Hf has 102 neutrons.

Elemental Hafnium is electrically neutral because it has the same amount of  positive charges (protons) and negative charges (electrons). Then, it must have 72 electrons.

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Answer:

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3 years ago
you are exploring the properties of a piece of matter you cut it in half several times which property of matter changes
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Only Extensive properties of piece will be changed. i.e Mass, Volume, Length etc.
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Your teacher asks you to follow the instructions in a lab to produce several known chemical reactions. During these procedures,
vova2212 [387]

Answer:

There are five evidences that tell whether a chemical change has occurred. These are change of color, change of odor, change in temperature or energy, formation of gas and formation of a precipitate.

Explanation:

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Let's have a further discussion of the evidences.

1. Change of Color- Color change is caused by the combination of two or more substance with different molecular structures. A popular example of this is the Statue of the Liberty, which is made of copper plates. Due to the exposure of copper to elements like water, it changed color.

2. Change of Odor- This can be best presented with rotting food. During the rotting process, the food undergoes a chemical reaction. The result is a rotten smell.

3. Change in Temperature or Energy- An example of this is the burning of wood. Its change is considered non-reversible.

4. Formation of Gas- This can be best presented with the cake batter (the one being used to make cakes or pancakes). The batter rises which means it is forming gas. This is caused by the reaction of the baking soda and the acid.

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3 0
3 years ago
How many Moles of NAOH are present in 2.50L of 0.300 M NaOH?
maw [93]
<h3>Answer:</h3>

0.75 moles NaOH

<h3>Explanation:</h3>

We are given;

Volume of NaOH solution = 2.5 Liters

Molarity of NaOH = 0.300 M

We are required to calculate the moles of NaOH

We need to establish the relationship between moles, molarity and volume of a solution.

That would be;

Concentration/molarity = Moles ÷ Volume

Therefore;

Moles = Concentration × Volume

Thus;

Moles of NaOH = 0.300 moles × 2.50 L

                         = 0.75 moles

Therefore, the number of moles of NaOH is 0.75 moles

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For the reaction shown, find the limiting reactant for each of the initial quantities of reactants.
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