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3 years ago

Use the periodic table to identify the chemical symbol or name for each element below.

Chemistry

2 answers:

Tom [10]3 years ago

4 0

Answer:yes

Explanation:yeaa

Rzqust [24]3 years ago

3 0

Answer:

zirconium is Zr

rhenium is Re

As is arsenic

K is potassium

tin is Sn

yttrium is Y

ytterbium is Yb

Explanation:

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Hurry up as fast as possible Ill mark you brainlist

Vika [28.1K]

It took 380,000 years for electrons to be trapped in orbits around nuclei, forming the first atoms.

These were mainly helium and hydrogen, which are still by far the most abundant elements in the universe. Present observations suggest that the first stars formed from clouds of gas around 150–200 million years after the Big Bang. Heavier atoms such as carbon, oxygen and iron, have since been continuously produced in the hearts of stars and catapulted throughout the universe in spectacular stellar explosions called supernovae.

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3 years ago

2 or more forces that are not equal and opposite of one another can cause change in motion

DedPeter [7]

Answer:

D unbalanced force

Explanation:

i think

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3 years ago

Determine the number of valence electrons for the following: [kr] 5s2 4d6

wlad13 [49]

Answer: B) 2 (as indicated by electron distribution shown), but taking into account the real properties of this element, 4,7,8 also occur (see below).

Explanation:

This is the electron complement/atomic number of ruthenium, which actually has the structure [Kr] 5s1 4d7

Nevertheless, Ru does not form Ru(I) compounds and few Ru(II) compounds (RuCl2, RuBr2, RuI2). It also forms Ru(III)Cl3 and a larger number of Ru(IV) compounds, e.g. RuO2, RuS2. It also forms RuO4

3 0

3 years ago

Th e molar absorption coeffi cient of a substance dissolved in water is known to be 855 dm3 mol−1 cm−1 at 270 nm. To determine t

Olegator [25]

Answer : The percentage reduction in intensity is 79.80 %

Explanation :

Using Beer-Lambert's law :

$A=\epsilon \times C\times l$

$A=\log \frac{I_o}{I}$

$\log \frac{I_o}{I}=\epsilon \times C\times l$

where,

A = absorbance of solution

C = concentration of solution = $3.25mmol.dm^{3-}=3.25\times 10^{-3}mol.dm^{-3}$

l = path length = 2.5 mm = 0.25 cm

$I_o$ = incident light

$I$ = transmitted light

$\epsilon$ = molar absorptivity coefficient = $855dm^3mol^{-1}cm^{-1}$

Now put all the given values in the above formula, we get:

$\log \frac{I_o}{I}=(855dm^3mol^{-1}cm^{-1})\times (3.25\times 10^{-3}mol.dm^{-3})\times (0.25cm)$

$\log \frac{I_o}{I}=0.6947$

$\frac{I_o}{I}=10^{0.6947}=4.951$

If we consider $I_o$ = 100

then, $I=\frac{100}{4.951}=20.198$

Here 'I' intensity of transmitted light = 20.198

Thus, the intensity of absorbed light $I_A$ = 100 - 20.198 = 79.80

Now we have to calculate the percentage reduction in intensity.

$\% \text{reduction in intensity}=\frac{I_A}{I_o}\times 100$

$\% \text{reduction in intensity}=\frac{79.80}{100}\times 100=79.80\%$

Therefore, the percentage reduction in intensity is 79.80 %

3 0

4 years ago

In an equimolar mixture of o2 and n2, are the mass fractions equal?

nika2105 [10]

Answer:

Explanation:

The mass fraction is defined as:

$w_{i}=\frac{m_{i} }{m_{t} }$

where:

wi: mass fraction of the substance i
mi: mass of the substance i
mt: total mass of the system

<u><em>The mass fraction of two substances (A and B), will be the same, ONLY if the mass of the substance A (mA) is the same as the mass of the substance B (mB).</em></u>

An equimolar mixutre of O2 and N2 has the same amount of moles of oxygen and nitrogen, just to give an example let's say that the system has 1 mole of O2 and 1 mole of N2. Then using the molecuar weigth of each of them we can calculate the mass:

mA= 1 mole of O2 * 16 g/1mol = 16 g

mB=1 mole of N2 *28 g/1mol=28 g

As mA≠mB then the mass fractions are not equal, so the answear is NO.

4 0

3 years ago