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2 years ago

How to round the number 314.77 to 2 significant figures

Chemistry

2 answers:

wariber [46]2 years ago

5 0

Answer:

发你如果热客人看看如果

Explanation:

aksik [14]2 years ago

3 0

Answer:

result = 310

significant figures = 2

Explanation:

How to round significant figures:

look the first non-zero digit if rounding to one significant figure, look the digit after the first non-zero digit if rounding to two significant figures. draw a vertical line after the place value digit that is required.look at the next digit.

result = 310

significant figures = 2

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Samantha AS

Anestetic [448]

Answer:

Fe(NO2)3

Explanation:

A poly atomic ion is an ion that contains more than one atom.

If we look at all the compounds that have been mentioned among the options; KBr and NaF are both ionic but do not contain any covalent poly atomic ion.

However, Fe(NO2)3 contains NO2^+ which is a poly atomic ion that contains the covalent bond.

8 0

2 years ago

1. The maximum recommended amount of citric acid (H3C6H5O7; the 3 hydrogens listed first are the acidic hydrogens – the only hyd

Lisa [10]

The density has been given as the mass of the substance per volume of the solution. The mass of citric acid in the bottle has been 1.22 grams.

<h3>What is percent mass?</h3>

Percent mass can be given as the mass of substance in the total mass of the solution.

The volume of the face serum has been 250 mL, and the density is 0.979 g/mL.

The mass of face serum in the bottle has been:

$\rm Density=\dfrac{Mass}{Volume}\\ 0.979\;g/mL=\dfrac{Mass}{250\;mL}\\ Mass=244.75\;g$

The total mass of face serum has been 244.75 grams.

The percent mass of citric acid in face serum is 0.5%. This states the presence of 0.5-gram citric acids in 100 grams sample.

The mass of citric acid in the face serum sample is given as:

$\rm 100\;gram\;sample=0.5\;g\;H_3C_6H_5O_7\\\\244.75\;grams\;sample=\dfrac{0.5}{100}\;\times\;244.75\;grams\; H_3C_6H_5O_7\\\\244.75\;grams\;sample=1.22\;grams\;H_3C_6H_5O_7$

The mass of citric acid present in 250 mL serum sample has been 1.22 grams.

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2 years ago

an electron in the 3rd shell of an Aluminium atom moves to the first shell in a bombardment process. Calculate the frequency of

Liula [17]

Following the quantic theory, the energy of a photon equals the radiation frequency multiplied by the universal constant. ν = 2.923x10¹⁵ Hz. E = 3.09x10¹⁵Hz.

<h3>What is quantum mechanic?</h3>

It is the branch of physics that studies objects and forces at a very low scale, at atoms, subatoms, and particles levels.

Quantum mechanics states that the elemental particles that constitute matter -electrons, neutrons, protons- have the properties of a wave and a particle.

It emerges from the quantic theory exposed by Max Planck (1922), in which he affirmed that light propagates in energy packages or photons.

He discovered the Universal Planck constant, h, used to calculate the energy of a photon.

He stated that the energy of a photon (E) equals the radiation frequency (ν) multiplied by the universal constant (h).

E = νh

In the exposed example, we need to calculate the energy required to change from the 3rd shell to the first shell.

To do it, we should know that the energy in a level (Eₙ) equals the energy associated to an electron in the most inferior energy level (E₁) divided by the square of the shell number (n²).

Eₙ = E₁ / n²

E₁ is a constant. We can express it in Joules or electroVolts

E₁ = -2.18x10⁻¹⁸ J
E₁ = -13.6 eV

So, let us calculate the energy at level 1 and 3

Eₙ = E₁ / n²

E₁ = -2.18x10⁻¹⁸ J / 1² = -2.18x10⁻¹⁸ J

E₁ = -13.6 eV / 1² = -13.6 eV

E₃ = -2.18x10⁻¹⁸ J / 3² = -2.18x10⁻¹⁸ J / 9 = - 2.42x10⁻¹⁹ J

E₃ = -13.6 eV / 3² = -13.6 eV / 9 = - 1.51 eV

The change of energy can be calculated in two ways,

Option 1

ΔE = E₁ - E₃ = 2.18x10⁻¹⁸ - 2.42x10⁻¹⁹ = 1.93x10⁻¹⁸J

ΔE = E₁ - E₃ = 13.6 - 1.51 = 12.09 eV

Option 2

ΔE = -2.18x10⁻¹⁸ J (1/nf² - 1/ni²)

ΔE =-13.6 eV (1/nf² - 1/ni²)

Where nf is the final level and ni is the initial level. When the electron passes from its initial level to its final level it is called electronic transition.

ni = 3
nf = 1

ΔE = -2.18x10⁻¹⁸ J (1/nf² - 1/ni²)

ΔE = -2.18x10⁻¹⁸ J (1/1² - 1/3²)

ΔE = -2.18x10⁻¹⁸ J (1 - 0.111)

ΔE = -2.18x10⁻¹⁸ J (0.888)

ΔE = - 1.937x10⁻¹⁸ J

ΔE = -13.6 eV (1/nf² - 1/ni²)

ΔE = -13.6 eV (1/1² - 1/3²)

ΔE = -13.6 eV (1 - 0.111)

ΔE = -13.6 eV (0.888)

ΔE = -12.08 eV

This is the energy required for the electron to go from n= 3 to n = 1. The negative sign (-) means energy (as light or photons) released or emitted.

If we want to express the result in Hz, we just need to make a conversion.

1Hz ⇔ 6.626x10⁻³⁴J ⇔ 4.136x10¹⁵ eV.

The energy required for the electron to go from n= 3 to n = 1 is 3.09x10¹⁵ Hz.

Now, we need to calculate the frequency, ν. This is, how many times the wave oscillates back and foward per second.

To do it, we will use the universal Planck constant, h, and the absolute value of the energy, E.

ν = E/h = 1.937x10⁻¹⁸ J / 6.626x10⁻³⁴ Js = 2.923x10¹⁵ 1/s = 2.923x10¹⁵ Hz.

Answer:

Frequency, ν = E/h = 2.923x10¹⁵ Hz.
Energy, E = 3.09x10¹⁵ Hz.

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5 0

1 year ago

A commercial oven with a book value of $67,000 has an estimated remaining 5 year life. A proposal is offered to sell the oven fo

baherus [9]

Answer:

$13,500

Explanation:

The differential analysis of the proposal to replace the commercial oven is shown below:-

The Total differential decrease in cost = Annual maintenance cost reduction × Number of years applicable

= $23,000 × 5

= $115,000

Inflow cash = The Total differential decrease in cost + Proceeds from sale of equipment

= 115,000 + $8,500

= $123,500

The Net differential decrease in cost from replacing equipment = Inflow cash - Cost of new equipment

= $123,500 - $110,000

= $13,500

8 0

2 years ago

An atom of fluorine has an atomic mass of 19 u. Keeping in mind that its atomic number is 9, what can you infer about this atom?

Oliga [24]

The fluorine atom has a neutron number of 10 it also have 10 valence electrons

8 0

3 years ago