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What type of a reaction takes place when atoms or molecules rearrange to form new substances

GREYUIT [131]

A chemical reaction happens when the atoms or molecules rearrange to form a new substance

6 0

3 years ago

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2074 Set B Q.No. 1 What mass of nitrogen will be requires

timurjin [86]

140 g of nitrogen (N₂)

Explanation:

We have the following chemical equation:

N₂ + 3 H₂ -- > 2 NH₃

Now, to find the number of moles of ammonia we use the Avogadro's number:

if 1 mole of ammonia contains 6.022 × 10²³ molecules

then X moles of ammonia contains 6.022 × 10²⁴ molecules

X = (1 × 6.022 × 10²⁴) / 6.022 × 10²³

X = 10 moles of ammonia

Taking in account the chemical reaction we devise the following reasoning:

If 1 mole of nitrogen produces 2 moles of ammonia

then Y moles of nitrogen produces 10 moles of ammonia

Y = (1 × 10) / 2

Y = 5 moles of nitrogen

number of moles = mass / molecular weight

mass = number of moles × molecular weight

mass of nitrogen (N₂) = 5 × 28 = 140 g

Learn more about:

Avogadro's number

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7 0

4 years ago

How many molecules are in 8.3 moles?

devlian [24]

1 mole=6.02 ×10

8.3 moles=?

8.3×6.02×10=499.66 molecules

therefore ghe no. of molecules = 499.66

6 0

3 years ago

What type of element has 8 electrons in their outer most level?

RideAnS [48]

Answer:

Noble gases

Explanation:

Neon and argon have 8 electrons in their outermost shells. The elements which have 8 electrons in the outermost shell or in the valence shell,are known as the noble gases.

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3 years ago

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Calculate the frequency of the n=2 line in the lyman series of hydrogen

Alona [7]

Answer:

Approximately $2.47\times 10^{15}\; \rm Hz$ .

Explanation:

The Lyman Series of a hydrogen atom are due to electron transitions from energy levels $n \ge 2$ to the ground state where $n = 1$ . In this case, the electron responsible for the line started at $n = 2$ and transitioned to

A hydrogen atom contains only one electron. As a result, Bohr Model provides a good estimate of that electron's energy at different levels.

In Bohr's Model, the equation for an electron at energy level $n$ (

$\displaystyle - \frac{k\, Z^2}{n^2}$ (note the negative sign in front of the fraction,)

where

$k = 2.179 \times 10^{-18}\; \rm J$ is a constant.

$Z$ is the atomic number of that atom. $Z = 1$ for hydrogen.
$n$ is the energy level of that electron.

The electron that produced the $n = 2$ line was initially at the

$\begin{aligned} &E_{n = 2} \cr &= -\frac{k\, Z^2}{n^2} \cr &= -\frac{2.179 \times 10^{-18} \times 1}{2^2} \cr & \approx -5.4475\times 10^{-19}\; \rm J\end{aligned}$ .

The electron would then transit to energy level $n = 1$ . Its energy would become:

$\begin{aligned} &E_{n = 1} \cr &= -\frac{k\, Z^2}{n^2} \cr &= -\frac{2.179 \times 10^{-18} \times 1}{1^2} \cr & \approx -2.179 \times 10^{-18} \; \rm J\end{aligned}$ .

The energy change would be equal to

$\begin{aligned}&\text{Initial Energy} - \text{Final Energy} \cr &= E_{n = 2} - E_{n = 1} \cr &= -5.4475 \times 10^{-19} - \left(-2.179 \times 10^{-18}\right) \cr & \approx 1.63425\times 10^{-18}\; \rm J \end{aligned}$ .

That would be the energy of a photon in that $n = 2$ spectrum line. Planck constant $h$ relates the frequency of a photon to its energy:

$E = h \cdot f$ , where

$E$ is the energy of the photon.
$h \approx 6.62607015\times 10^{-34}\; \rm J \cdot s$ is the Planck constant.
$f$ is the frequency of that photon.

In this case, $E \approx 1.63425 \times 10^{-18}\; \rm J$ . Hence,

$\begin{aligned} f &= \frac{E}{h} \cr &\approx \frac{1.63425\times 10^{-18}}{6.62607015\times 10^{-34}} \cr & \approx 2.47 \times 10^{15}\; \rm s^{-1}\end{aligned}$ .

Note that $1 \; \rm Hz = 1 \; \rm s^{-1}$ .

6 0

4 years ago