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3 years ago

Which is the same length as a light-year?

Chemistry

2 answers:

Ilya [14]3 years ago

7 0

A the distance light travels in one year is the correct answer I took the test

andrew11 [14]3 years ago

5 0

Answer:

Explanation:

Just A...

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11. Which of the following best explains why CO2 gas is easily compressible but solid

Oduvanchick [21]

Answer:

The right answer is C. The molecules of solid CO2 are much closer together than the molecules of CO2 gas.

8 0

4 years ago

After 15 minutes, 30 g of a sample of polonium-218 remain unchanged. If the original sample had a mass of 960 g, what is the hal

Keith_Richards [23]

Q1. The answer is 3 minutes.

Let's first calculate the remaining amount in percent:
If 960g is 100 percent (starting amount), 30 g is how many percents:
960 g : 100% = 30 g : x
x = 30 g * 100% / 960 g = 3.125% = 0.03125

Now, using the formula to calculate the number of half-lives:
(1/2)ⁿ = x,
where
x is the remaining amount: x = 0.03125
n is the number of half-lives
1/2 stands for half-life.

(1/2)ⁿ = 0.03125
⇒ n*log(1/2) = log(0.03125)
n = log(0.03125)/log(1/2) = log(0.03125)/log(0.5) = -1.505/-0.301 ≈ 5

The number of half-lives is 5.
Now, the number of half-lives (n) is a quotient of total time elapsed (T) and length of half-life (L):
n = T/L
We know:
n = 5
T = 15 min
L = ?

Thus
L = T/n
L = 15 min/5 = 3 minutes

Q2. Filtration should be chosen.
Filtration and distillation are used to separate mixtures - filtration for the separation of heterogeneous mixtures and distillation for the separation of homogeneous mixtures. Imagine that your pile of soil is a mixture. It consists of different components (the leaves, acorns, twigs), so it is the heterogeneous mixture. Therefore, to separate the leaves, acorns, twigs you will use filtration.

5 0

4 years ago

An electron in an atom is known to be in a state with magnetic quantum number ml=−1

Ulleksa [173]

Explanation:

It is known that the maximum value of ml is equal to the vale of l. But the minimum value of n is as follows.

n = l + 1

where, n = principle quantum number

l = azimuthal quantum number

Values of n can be 1, 2, 3, 4 and so on. Whereas the values of l can be 0, 1, 2, 3, and so on.

Also, "m" is known as magnetic quantum number whose values can be equal to -l and +l.

So, when n = 1 then l = 0 and m = 0.

When n = 2 then l = 1 and values of m will be equal to -1, 0, +1. As it is given that the magnetic quantum number ml = -1. Hence, it is only possible when n = 2.

Thus, we can conclude that the smallest possible value of the principal quantum number n of the state is 2.

5 0

3 years ago

What mass of water vapor is produced from the gas phase reaction of O2 with H2 in a 2.5 L container at 28 °C if the partial pres

Bumek [7]

Answer:2.27 g H2O

Explanation:

Step 1. Get the limiting reagent

1.24 atm of H2 would react completely with 1.24 x (1/2) = 0.62 atm of O2, but there is more O2 present than that (0.98). O2 is in excess and H2 is the limiting reactant.

If the reaction goes to completion:

(1.24 atm H2) x (2 mol H2O / 2 mol H2) = 1.24 atm H2O vapor

n = PV / RT = (1.24 atm) x (2.5 L) / ((0.08205746 L atm/K mol) x (28 + 273)K) = 0.126 mol H2O

(0.126 mol H2O) x (18.01532 g H2O/mol) = 2.27 g H2O

3 0

3 years ago

Read 2 more answers

Buffer preparation. You wish to prepare a buffer consisting of acetic acid and sodium acetate with a total acetic acid plus acet

Hoochie [10]

Answer:

0.182 moles of acetic acid are needed, this means 10.93 g.

0.318 moles of sodium acetate are needed, this means 26.08 g.

Explanation:

The Henderson–Hasselbalch (H-H) equation tells us the relationship between the concentration of an acid, its conjugate base, and the pH of a buffer:

pH = pka + $log\frac{[A^{-} ]}{[HA]}$

In this case, [A⁻] is the concentration of sodium acetate, and [HA] is the concentration of acetic acid. The pka is a value that can be looked up in literature: 4.76.

From the problem we know that

[A⁻] + [HA] = 250 mM = 0.250 M eq. 1

We use the H-H equation, using the data we know, to describe [A⁻] in terms of [HA]:

5.0 = 4.76 + $log\frac{[A^{-} ]}{[HA]}$

$0.24=log\frac{[A^{-} ]}{[HA]}\\\\10^{0.24}=\frac{[A^{-} ]}{[HA]}\\ 1.74 [HA] = [A^{-}]$ eq.2

Now we replace the value of [A⁻] in eq. 1, to calculate [HA]:

1.74 [HA] + [HA] = 0.250 M

[HA] = 0.091 M

Then we calculate [A⁻]:

[A⁻] + 0.091 M = 0.250 M

[A⁻] = 0.159 M

Using the volume, we can calculate the moles of each substance:

moles of acetic acid = 0.091 M * 2 L = 0.182 moles
moles of sodium acetate = 0.159 M * 2 L = 0.318 moles

Using the molecular weight, we can calculate the grams of each substance:

grams of acetic acid = 0.182 mol * 60.05 g/mol = 10.93 g
grams of sodium acetate = 0.318 mol * 82.03 g/mol = 26.08 g

8 0

3 years ago