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3 years ago

7

For centuries, sailors used tree sap (pitch) to seal the spaces between the planks on wooden boats. Explain why pitch worked wel

l as a sealant in this situation

1 answer:

o-na [289]3 years ago

5 0

Tree sap is a viscoelastic polymer, which means it's not really a solid but a very viscous (sticky) fluid. It's fluidity ensures that it can properly <span>seal the spaces between the planks on wooden boats. Not only that, the pitch sap is hydrophobic - it is water resistant as well. </span>

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What is the molarity when water is added to 4 moles of sodium chloride to make 0.5 liter of solution?

loris [4]

If 0.5 L of solution contains 4 mol
then let 1 L of solution contain x mol

⇒ (0.5 L) x = (4 mol) (1 L)

x = (4 mol · L) ÷ (0.5 L)

x = 8 mol

Thus the molarity of the Sodium Chloride solution is 8 mol / L OR 8 mol/dm³.

7 0

3 years ago

A 20 g granite boulder absorbs 300.2 Joules of energy from the Sun, resulting in its temperature

s344n2d4d5 [400]

Answer:

19 °C

Explanation:

Step 1: Given and required data

Mass of granite (m): 20 g

Heat absorbed (Q): 300. 2 J

Specific heat capacity of granite (c): 0.790 J/g.°C

Step 2: Calculate the temperature change (ΔT)

We will use the following expression.

Q = c × m × ΔT

ΔT = Q/c × m

ΔT = 300.2 J/(0.790 J/g.°C) × 20 g = 19 °C

3 0

3 years ago

Be sure to answer all parts. The standard enthalpy of formation and the standard entropy of gaseous benzene are 82.93 kJ/mol and

skelet666 [1.2K]

Answer : The values of $\Delta H^o,\Delta S^o\text{ and }\Delta G^o$ are $33.89kJ,95.94J/K\text{ and }5.299kJ/mol$ respectively.

Explanation :

The given balanced chemical reaction is,

$C_6H_6(l)\rightarrow C_6H_6(g)$

First we have to calculate the enthalpy of reaction $(\Delta H^o)$ .

$\Delta H^o=H_f_{product}-H_f_{reactant}$

$\Delta H^o=[n_{C_6H_6(g)}\times \Delta H_f^0_{(C_6H_6(g))}]-[n_{C_6H_6(l)}\times \Delta H_f^0_{(C_6H_6(l))}]$

where,

$\Delta H^o$ = enthalpy of reaction = ?

n = number of moles

$\Delta H_f^0_{(C_6H_6(g))}$ = standard enthalpy of formation of gaseous benzene = 82.93 kJ/mol

$\Delta H_f^0_{(C_6H_6(l))}$ = standard enthalpy of formation of liquid benzene = 49.04 kJ/mol

Now put all the given values in this expression, we get:

$\Delta H^o=[1mole\times (82.93kJ/mol)]-[1mole\times (49.04J/mol)]$

$\Delta H^o=33.89kJ/mol=33890J/mol$

Now we have to calculate the entropy of reaction $(\Delta S^o)$ .

$\Delta S^o=S_f_{product}-S_f_{reactant}$

$\Delta S^o=[n_{C_6H_6(g)}\times \Delta S^0_{(C_6H_6(g))}]-[n_{C_6H_6(l)}\times \Delta S^0_{(C_6H_6(l))}]$

where,

$\Delta S^o$ = entropy of reaction = ?

n = number of moles

$\Delta S^0_{(C_6H_6(g))}$ = standard entropy of formation of gaseous benzene = 269.2 J/K.mol

$\Delta S^0_{(C_6H_6(l))}$ = standard entropy of formation of liquid benzene = 173.26 J/K.mol

Now put all the given values in this expression, we get:

$\Delta S^o=[1mole\times (269.2J/K.mol)]-[1mole\times (173.26J/K.mol)]$

$\Delta S^o=95.94J/K.mol$

Now we have to calculate the Gibbs free energy of reaction $(\Delta G^o)$ .

As we know that,

$\Delta G^o=\Delta H^o-T\Delta S^o$

At room temperature, the temperature is $25^oC\text{ or }298K$ .

$\Delta G^o=(33890J)-(298K\times 95.94J/K)$

$\Delta G^o=5299.88J/mol=5.299kJ/mol$

Therefore, the values of $\Delta H^o,\Delta S^o\text{ and }\Delta G^o$ are $33.89kJ,95.94J/K\text{ and }5.299kJ/mol$ respectively.

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3 years ago

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How does the type of medium affect a sound wave? Give an Example

ivanzaharov [21]

Answer:

Sound waves need to travel through a medium such as solids, liquids and gases. The sound waves move through each of these mediums by vibrating the molecules in the matter. The molecules in solids are packed very tightly. Liquids are not packed as tightly.Of the three mediums (gas, liquid, and solid) sound waves travel the slowest through gases, faster through liquids, and fastest through solids. Temperature also affects the speed of sound.Sound waves in air (and any fluid medium) are longitudinal waves because particles of the medium through which the sound is transported vibrate parallel to the direction that the sound wave moves. A vibrating string can create longitudinal waves as depicted in the animation below.

Explanation:

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3 years ago

What is incorrect in the structure? Check all that apply. The middle hydrogen is surrounded by 4 electrons. Oxygen is surrounded

Veronika [31]

Answer: The middle hydrogen is surrounded by 4 electrons, the middle hydrogen is bonded to 2 elements, and there are too many electrons in the final structure are correct.

Explanation: I just did this question and got the correct answers.

6 0

3 years ago

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