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3 years ago

Is li, an, and k a group or period

Chemistry

1 answer:

rodikova [14]3 years ago

7 0

Answer:

they are elements

Explanation:

li- lithium

an- alluminum

k- potassium

a period runs horzontal within the tabel and the groups run vertcle

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A compound is found to contain 38.65 % carbon, 16.25 % hydrogen, and 45.09 % nitrogen by mass. what is the empirical formula for

iren [92.7K]

The molar mass of carbon is 12, hydrogen is 1, and nitrogen is 14, hence the ratio are:

C = 38.65 / 12 = 3.22

H = 16.25 / 1 = 16.25

N = 45.09 / 14 = 3.22

Divide the three by the lowest ratio which is 3.22:

C = 3.22 / 3.22 = 1

H = 16.25 / 3.22 = 5

N = 3.22 / 3.22 = 1

So the empirical formula is:

CHN

5 0

3 years ago

If the initial [NO2] is 0.260 M, it will take ________ s for the concentration to drop to 0.150 M. If the initial is 0.260 , it

Nitella [24]

The question is incomplete, here is the complete question:

At elevated temperature, nitrogen dioxide decomposes to nitrogen oxide and oxygen gas

$NO_2\rightarrow NO+\frac{1}{2}O_2$

The reaction is second order for $NO_2$ with a rate constant of $0.543M^{-1}s^{-1}$ at 300°C. If the initial [NO₂] is 0.260 M, it will take ________ s for the concentration to drop to 0.150 M

a) 1.01 b) 5.19 c) 0.299 d) 0.0880 e) 3.34

Answer: The time taken is 5.19 seconds

Explanation:

The integrated rate law equation for second order reaction follows:

$k=\frac{1}{t}\left (\frac{1}{[A]}-\frac{1}{[A]_o}\right)$

where,

k = rate constant = $0.543M^{-1}s^{-1}$

t = time taken = ?

[A] = concentration of substance after time 't' = 0.150 M

$[A]_o$ = Initial concentration = 0.260 M

Putting values in above equation, we get:

$0.543=\frac{1}{t}\left (\frac{1}{(0.150)}-\frac{1}{(0.260)}\right)\\\\t=5.19s$

Hence, the time taken is 5.19 seconds

6 0

4 years ago

2. Explain why sedimentary rock layers of the North and South Rim(side) of the Grand Canyon are the same age, using Steno’s Prin

natali 33 [55]

Answer:

Law of Lateral Continuity The Grand Canyon.

and

he same rock layers on opposite sides of the canyon. The matching rock layers were deposited at the same time, so they are the same age.

3 0

3 years ago

The mass of solute per 100 mL of solution is abbreviated as (m/v). Mass is not technically the same thing as weight, but the abb

Nimfa-mama [501]

Answer:

$\boxed{\text{254 g}}$

Explanation:

$\begin{array}{rcl}\text{\% m/V} & = & \dfrac{\text{Mass of sucrose}}{\text{Volume of solution}}\\\\\text{Let m}& = &\text{mass of sucrose}\\\dfrac{\text{35.0 g}}{\text{100 mL}}& = & \dfrac{m}{\text{725 mL}}\\\\m & = &\dfrac{\text{35.0 g}\times 725}{100}\\\\ & = &\textbf{254 g}\\\end{array}\\\text{You need $\boxed{\textbf{254 g}}$ of sucrose}$

3 0

4 years ago

In which of the following compounds does the carbonyl stretch in the IR spectrum occur at the lowest wavenumber?

klio [65]

Answer:

a. Cyclohexanone

Explanation:

The principle of IR technique is based on the vibration of the bonds by using the energy that is in this region of the electromagnetic spectrum. For each bond, there is a specific energy that generates a specific vibration. In this case, you want to study the vibration that is given in the carbonyl group C=O. Which is located around 1700 cm-1.

Now, we must remember that the lower the wavenumber we will have less energy. So, what we should look for in these molecules, is a carbonyl group in which less energy is needed to vibrate since we look for the molecule with a smaller wavenumber.

If we look at the structure of all the molecules we will find that in the last three we have heteroatoms (atoms different to carbon I hydrogen) on the right side of the carbonyl group. These atoms allow the production of resonance structures which makes the molecule more stable. If the molecule is more stable we will need more energy to make it vibrate and therefore greater wavenumbers.

The molecule that fulfills this condition is the cyclohexanone.

See figure 1

I hope it helps!

4 0

4 years ago