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2 years ago

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]2 years ago

7 0

178 of each species
178 protons
178 neutrons
And 178 electrons

AlladinOne [14]2 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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2 years ago

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Explanation:

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2 years ago

Calculate the mass of CO2 that can be produced if the reaction of 54.0 g of propane and sufficient oxygen has a 64.0% yield.

Oduvanchick [21]

Answer:

103.9 g

Explanation:

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

First we convert 54.0 g of propane (C₃H₈) into moles, using its molar mass:

54.0 g ÷ 44 g/mol = 1.23 mol C₃H₈

Then we convert 1.23 moles of C₃H₈ into moles of CO₂, using the stoichiometric coefficients:

1.23 mol C₃H₈ * $\frac{3molCO_2}{1molC_3H_8}$ = 3.69 mol CO₂

We convert 3.69 moles of CO₂ into grams, using its molar mass:

3.69 mol CO₂ * 44 g/mol = 162.36 g

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2 years ago