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3 years ago

What physical effect can change the boiling point of a substance?

2 answers:

5 0

The correct answer for the following questions that are presented above are these ones:
(1) b. Pressure. The <span>physical effect can change the boiling point of a substance is the pressure.
(2) </span><span>Evaporation only occurs at the surface of a liquid. TRUE.</span><span>
(3) </span>d. freezing. The change from liquid to solid, or the reverse of melting, is called freezing.

Nesterboy [21]3 years ago

5 0

Answer 1:The correct answer is option b.

Explanation:

A boiling of the liquid is temperature at which the vapor pressure of the liquid becomes equal to the pressure exerted by the gas above it.

If the pressure of gas is 1 atm the liquid will boil at its normal boiling point.
If the pressure of the gas is less than that of the 1 atm than the liquid will boil at temperature lower than its normal boiling point.
If the pressure of the gas is more than 1 atm than the liquid will boil at temperature higher than its normal boiling point.

Evaporation is defined as surface process where water molecules from liquid state are converted into gaseous state from the surface of the liquid.

Answer 2:The correct answer is option d.

Explanation:

Freezing: It is a process in which liquid state of matter is converted into solid state of the matter.

Liquid state → Solid state

Condensation :The change of state of matter from gaseous state to liquid state is termed a condensation.

Boiling: It is a process by which a liquid is turned into a vapors by providing heat to the liquid.

Sublimation:The change of state of matter from solid state to gaseous state by escaping liquid state is termed a sublimation.

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A compound with molecular formula C6H15N exhibits a singlet at d 0.9 ppm (1H), a triplet at 1.10 ppm (3H), a singlet at 1.15 ppm

Triss [41]

Answer:

CH3 - CH2 - NH - C(CH3)3

Explanation:

The 1HNMR is the acronym for Proton nuclear magnetic resonance and it is used in chemistry or Chemical laboratory for the analysis and identification of compounds.

In order to be able to answer the question accurately you have to have the tables containing all the values for chemical shift. The Chemical shift is measured in ppm and it occur due to Resonance frequency variation.

From the table, a singlet at 1.15 ppm (9H) is - C(CH3)3.

A singlet at d 0.9 ppm (1H) shows the presence of a secondary amine group, that is -R2NH group.

A triplet at 1.10 ppm (3H) shows that we have;

CH3- CH2-

A quartet at 2.6 ppm (2H) shows that we have;

-CH2 - CH3.

Therefore, joining all together we have;

CH3 - CH2 - NH - C(CH3)3.

Kindly check attached file for the picture of the structure.

5 0

2 years ago

If kinetic energy increases does pressure decrease?

enyata [817]

If molecules are in a closed container then we expect the pressure to increase as the kinetic energy increases. This is because the atoms of an element collide with the walls of the container and increase the pressure.

If we use the formula $PV=nRT$ , where P is the pressure, V is the volume, n is the number of moles, R the ideal gas constant and T is the temperature. According to the formula, P is directly proportional to temperature. An increase in temperature leads to an increase in pressure.

Since we know that temperature is the average kinetic energy of molecules present. It means as we increase the temperature we increase the kinetic energy of the molecules which in turn leads to an increase in the pressure.

8 0

3 years ago

Given these reactions, where X represents a generic metal or metalloid 1 ) H 2 ( g ) + 1 2 O 2 ( g ) ⟶ H 2 O ( g ) Δ H 1 = − 241

anygoal [31]

Answer : The enthalpy of the given reaction will be, -1048.6 kJ

Explanation :

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

The main reaction is:

$XCl_4(s)+2H_2O(l)\rightarrow XO_2(s)+4HCl(g)$ $\Delta H=?$

The intermediate balanced chemical reactions are:

(1) $H_2(g)+\frac{1}{2}O_2(g)\rightarrow H_2O(g)$ $\Delta H_1=-241.8kJ$

(2) $X(s)+2Cl_2(g)\rightarrow XCl_4(s)$ $\Delta H_2=+461.9kJ$

(3) $\frac{1}{2}H_2(g)+\frac{1}{2}Cl_2(g)\rightarrow HCl(g)$ $\Delta H_3=-92.3kJ$

(4) $X(s)+O_2(g)\rightarrow XO_2(s)$ $\Delta H_4=-789.1kJ$

(5) $H_2O(g)\rightarrow H_2O(l)$ $\Delta H_5=-44.0kJ$

Now reversing reaction 2, multiplying reaction 3 by 4, reversing reaction 1 and multiplying by 2, reversing reaction 5 and multiplying by 2 and then adding all the equations, we get :

(1) $2H_2O(g)\rightarrow 2H_2(g)+O_2(g)$ $\Delta H_1=2\times 241.8kJ=483.6kJ$

(2) $XCl_4(s)\rightarrow X(s)+2Cl_2(g)$ $\Delta H_2=-461.9kJ$

(3) $2H_2(g)+2Cl_2(g)\rightarrow 4HCl(g)$ $\Delta H_3=4\times -92.3kJ=-369.2kJ$

(4) $X(s)+O_2(g)\rightarrow XO_2(s)$ $\Delta H_4=-789.1kJ$

(5) $2H_2O(l)\rightarrow 2H_2O(g)$ $\Delta H_5=2\times 44.0kJ=88.0kJ$

The expression for enthalpy of main reaction will be:

$\Delta H=\Delta H_1+\Delta H_2+\Delta H_3+\Delta H_4+\Delta H_5$

$\Delta H=(483.6)+(-461.9)+(-369.2)+(-789.1)+(88.0)$

$\Delta H=-1048.6kJ$

Therefore, the enthalpy of the given reaction will be, -1048.6 kJ

4 0

2 years ago

Why edible oils shows rancidity when stored for a long time

iren2701 [21]

When edible oils are idle and stored for a long amount of time, they undergo oxidation due to the exposure to oxygen. This oxidation causes rancidity in oils.

4 0

3 years ago

3 points

VLD [36.1K]

Answer:

<h3>The answer is 8.29 %</h3>

Explanation:

The percentage error of a certain measurement can be found by using the formula

$P(\%) = \frac{error}{actual \: \: number} \times 100\% \\$

From the question

actual density = 19.30g/L

error = 20.9 - 19.3 = 1.6

We have

$p(\%) = \frac{1.6}{19.3} \times 100 \\ = 8.290155440...$

We have the final answer as

Hope this helps you

5 0

3 years ago