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3 years ago

Answer each of the following questions with increases, decreases, or does not change.

Chemistry

1 answer:

Nitella [24]3 years ago

7 0

Answer:

a) increases

b) decreases

c) does not change

d) increases

Explanation:

The vapour pressure of a liquid is dependent on;

I) the magnitude of intermolecular forces

II) the temperature of the liquid

Hence, when any of these increases, the vapour pressure increases likewise.

Similarly, the boiling point of a liquid depends on the magnitude of intermolecular forces present because as intermolecular forces increases, more energy is required to break intermolecular bonds.

Lastly, increase in surface area of a liquid does not really affect it's vapour pressure.

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Calculate the ph of a 0.021 m nacn solution. [ka(hcn) = 4.9  10–10]

ohaa [14]

Answer is: pH of solution of sodium cyanide is 11.3.
Chemical reaction 1: NaCN(aq) → CN⁻(aq) + Na⁺(aq).
Chemical reaction 2: CN⁻ + H₂O(l) ⇄ HCN(aq) + OH⁻(aq).
c(NaCN) = c(CN⁻) = 0.021 M.
Ka(HCN) = 4.9·10⁻¹⁰.
Kb(CN⁻) = 10⁻¹⁴ ÷ 4.9·10⁻¹⁰ = 2.04·10⁻⁵.
Kb = [HCN] · [OH⁻] / [CN⁻].
[HCN] · [OH⁻] = x.
[CN⁻] = 0.021 M - x..
2.04·10⁻⁵ = x² / (0.021 M - x).
Solve quadratic equation: x = [OH⁻] = 0.00198 M.
pOH = -log(0.00198 M) = 2.70.
pH = 14 - 2.70 = 11.3.

4 0

3 years ago

Please answer he questions

Nastasia [14]

"Work done by a constant force on an object is the product of the force and the distance moved by the object in the direction of the force" -textbook

There is work done ONLY if the direction of the force and the direction the item is moving are the same. In figure A, the direction of the force (the lifting) is upwards (defying gravity), and the book is moving upwards, so work is done. In figure B, the force is still moving upwards (the person is carrying the books) but the book is moving to the right, so there is NO work done.

6 0

3 years ago

At 20°C the vapor pressure of benzene (C6H6) is 75 torr, and that of toluene (C7H8) is 22 torr. Assume that benzene and toluene

valina [46]

Answer: The mole fraction of benzene will be 0.34 and mole fraction of toluene is 0.66

Explanation:

According to Raoult's law, the vapor pressure of a component at a given temperature is equal to the mole fraction of that component multiplied by the vapor pressure of that component in the pure state.

$p_1=x_1p_1^0$ and $p_2=x_2P_2^0$

where, x = mole fraction in solution

$p^0$ = pressure in the pure state

According to Dalton's law, the total pressure is the sum of individual pressures.

$p_{total}=p_1+p_2\\$ $p_{total}=x_{benzene}p_{benzene}^0+x_{toluene}P_{toluene}^0$

$x_{benzene}=x$ ,

$x_{toluene}=1-x_{benzene}=1-x$ ,

$p_{benzene}^0=75torr$

$p_{toluene}^0=22torr$

$p_{total}=40torr$

$40=x\times 75+(1-x)\times 22$

$x=0.34$

Thus (1-x0 = (1-0.34)=0.66

Thus the mole fraction of benzene will be 0.34 and that of toluene is 0.66

8 0

3 years ago

Write the condensed nd structural formulas as well as the names for all isomers of C3H5Cl3.

Sergio039 [100]

Answer:

1) 1,1,1-trichloropropane

2) 1,1,2-trichloropropane

3) 1,2,2-trichloropropane

4) 1,2,3-trichloropropane

Explanation:

For this question, we must remember that isomers are molecules that have the same formula but different structures. For the formula $C_3H_5Cl_3$ we can draw a linear chain of three carbons and change the position of the chlorine atoms in the carbon chain.

With this in mind, if we put all the chlorine atoms on the same carbon we will get 1,1,1-trichloropropane. If we change an atom from chlorine to carbon 2 we will obtain 1,1,2-trichloropropane. If we move another chlorine atom to carbon two we will get 1,2,2-trichloropropane. Finally, if we put a chlorine atom in each carbon we will obtain 1,2,3-trichloropropane.

See figure one for further explanations

I hope it helps!

4 0

3 years ago

Promethium-147 is sometimes used in luminescent paint. It has a half-life of 956.3 days. If 250 grams (g) of promethium-147 is u

Fantom [35]

Answer:

% = 76.75%

Explanation:

To solve this problem, we just need to use the expressions of half life and it's relation with the concentration or mass of a compound. That expression is the following:

A = A₀ e^(-kt) (1)

Where:

A and A₀: concentrations or mass of the compounds, (final and initial)

k: constant decay of the compound

t: given time

Now to get the value of k, we should use the following expression:

k = ln2 / t₁/₂ (2)

You should note that this expression is valid when the reaction is of order 1 or first order. In this kind of exercises, we can assume it's a first order because we are not using the isotope for a reaction.

Now, let's calculate k:

k = ln2 / 956.3

k = 7.25x10⁻⁴ d⁻¹

With this value, we just replace it in (1) to get the final mass of the isotope. The given time is 1 year or 365 days so:

A = 250 e^(-7.25x10⁻⁴ * 365)

A = 250 e^(-0.7675)

A = 191.87 g

However, the question is the percentage left after 1 year so:

% = (191.87 / 250) * 100

<h2>% = 76.75%</h2><h2>And this is the % of isotope after 1 year</h2>

3 0

3 years ago

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