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2 years ago

Assertion (A): Naphthalene balls disappear with time without leaving any solid.

Chemistry

2 answers:

gogolik [260]2 years ago

7 0

Explanation:

a) Both A and R are true and R is the correct

explanation of A.

Kruka [31]2 years ago

7 0

Answer:

$\fbox {c) A is true but R is false.}$

Explanation:

Assertion (A):

⇒ Naphthalene balls disappear with time without leaving any solid.

⇒ True √

Reason (R):

⇒ Solid converted to liquid is called sublimation.

⇒ False ×

⇒ Solid converted to liquid is called melting

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The average propane cylinder for a residential grill holds approximately 18 kg of propane. how much energy (in kj) is released b

Angelina_Jolie [31]

Let's begin with the basic values that will be used in the solution.

The formula of propane is C3H8. It is an alkane, a hydrocarbon with the general formula of CnH2n+2. Notice that hydrocarbons have only Carbon and Hydrogen atoms. Its molar mass (M) is 44 g.

Molar Mass Calculation is done as like that
C=12 g/mol, H=1 g/mol. 1 mole propane has 3 moles Carbon atoms and 8 mole Hydrogen atoms. M(C3H8)= 3*12+ 8*1= 44 g

Combustion reaction of hydrocarbons gives carbon dioxide and water by releasing energy. That energy is called as enthalpy of combustion (ΔHc°).

ΔHc° of propane equals -2202.0 kj/mol. Burning of 1 mole C3H8 releases 2202 kj energy. Minus sign only indicates that the energy is given out ( an exothermic reaction ).

Let's write the combustion reaction.
C3H8 + O2 ---> CO2 + H20 (unbalanced) ΔHc° = -2202 kj/mol

Now, we calculate mole of 20 kg propane. Convert kilogram into gram since we use molar mass is defined in grams.
mole=mass/molar mass ; n=m/M ; n= 20000 g /44 (g/mol)=454 mole

1 mole propane releases 2202 kj energy.
454 mole propane release 2202 kj *454= 1000909 kj

The answer is 1000909 kj.

6 0

4 years ago

Calculate the magnitude and direction (i.e., the angle with respect to the positive H-axis, measured positive as counter-clockwi

r-ruslan [8.4K]

The graphics in the attachment is part of the question, which was incomplete.

Answer: Fr = 102N and angle of approximately 11°.

Explanation: From the attachment, it is observed that from the three forces acting on M, two are perpendicular. So to find them, we have to show their x- and y- axis components. From the graph:

Fx = 70+40-10 = 100

Fy = 40-20 = 20

Now, as the forces form a triangle, the totalforce is:

Fr = $\sqrt{Fx^{2} +Fy^{2} }$

Fr = $\sqrt{10400}$

Fr = ≈ 102N

To determine the angle requested, we use:

arctg H = $\frac{Fy}{Fx}$

arctg H = $\frac{20}{100}$

H = tg 0.2 ≈ 11°.

4 0

4 years ago

A 1.87 L aqueous solution of KOH contains 155 g of KOH . The solution has a density of 1.29 g/mL . Calculate the molarity ( M ),

Semenov [28]

Answer:

[KOH] : 1.47 M

[KOH] : 1.22 m

[KOH]: 6.42 % mass percent.

Explanation:

First of all we must determine the volume of solution. We have to work with the density

Density = mass / volume

1.29 g/ml = mass / 1870 ml

1.29 g/ml . 1870 ml = 2412.3

Now we must convert the mass to moles

155g / 56.1 g/ mol = 2.76 moles

Now we can calculate molarity

2.76 mol / 1.87 L = 1.47 M

To calculate molality we have to find out the mass of solvent

mass solute + mass solvent = mass solution

155 g + mass solvent = 2412.3 g

2412.3g - 155g = 2257.3g

We have to convert the 2257.3 g to kg

2257.3 g = 2.25 kg

molality = 2.76 moles / 2.25 kg = 1.22 m

To find out the % mass percentation, we have to calculate the mass of solute in 100 g of solution.

In 2412.3 g of solution we have 155 g of KOH

In 100 g of solution, we would have (100 . 155) / 2412.3 = 6.42 %mass percent.

7 0

3 years ago

What is true about resonance structures? Select the correct answer below: They are all different molecules. The interconvert wit

3241004551 [841]

Answer:

The correct answer is: They each partially describe the bonding in a molecule.

Explanation:

Some chemical molecules cannot be described completely by using only one Lewis structure. In these cases, we can describe the molecule by drawing 2 or more Lewis structures, and the structures are called resonance structures. The overall molecular structure is explained by all the resonance structures together. So, they each describe the bonding in the molecule only partially.

7 0

3 years ago

How many atoms are in 3.0 moles of NA?

Vanyuwa [196]

Avogadro's number is the number of atoms in one mole of a substance. The number is 6.022 x 10^23 atoms/mol. So, if you have 1 mole of carbon atoms, there will be 6.022 x 10^23 atoms in that sample.

Hope this helps

5 0

3 years ago