CHEMISTRY HIGH SCHOOL

The change in heat energy for a reaction is best expressed as a change in a. Enthalpy (H)
b. Absolute temperature (T)
c. Specific heat (c)
d. Entropy (S)
e. Kinetic energy (KE)

Answers

Answer 1
Answer: If the reaction is at constant pressure then it is a. Enthalpy

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A scientist heats a flexible container full of neon gas. What will most likely happen to the container as the gas absorbs heat?It will shrink, because the neon atoms will break apart into smaller pieces.

It will expand, because the neon atoms will get larger.

It will expand, because the neon atoms will move more quickly and get farther apart.

It will shrink, because the neon atoms will lose energy as heat, and move closer together.

Answers

As you heat gas up, the molecules move more rapidly. This pushes harder on the outside of the container, forcing it to expand. Atoms do not change in size. 
So, the answer to the second question is C. It will expand because the neon atoms will move more quickly and get farther apart.

Answer: It will expand, because the neon atoms will move more quickly and get farther apart.

Explanation: This can be explained based on Charle's law.

Charles' Law: This law states that volume is directly proportional to the temperature of the gas at constant pressure and number of moles.


V\propto T    (At constant pressure and number of moles)

Thus if a gas absorbs heat at constant pressure and no of moles, the temperature of the gas increases and thus the volume also increases and thus it expands by gaining kinetic energy and moving far apart.

The Haber process can be used to produce ammonia (NH3) from hydrogen gas (H2) and nitrogen gas (N2). The balanced equation for this process is shown below.3H2 + N2 mc025-1.jpg 2NH3

The molar mass of NH3 is 17.03 g/mol. The molar mass of H2 is 2.0158 g/mol. In a particular reaction, 0.575 g of NH3 forms. What is the mass, in grams, of H2 that must have reacted, to the correct number of significant figures?
0.1
0.102
0.10209
0.1021

Answers

Answer : The mass of H_2 in grams is 0.102g.

Solution : Given,

Molar mass of NH_3 = 17.03 g/mole

Molar mass of H_2 = 2.0158 g/mole

Given Mass of NH_3 = 0.575 g

First we have to calculate the moles of NH_3.

\text{ Moles of }NH_3=\frac{\text{ Given mass of }NH_3}{\text{ Molar mass of }NH_3} = (0.575g)/(17.03g/mole) = 0.0337 moles

The given balanced equation is,

3H_2(g)+N_2(g)\rightarrow 2NH_3(g)

From the above reaction, we conclude that

2 moles of NH_3 produced from 3 moles of H_2

then the 0.0337 moles of NH_3 produces to give (3moles* 0.0337moles)/(2moles) moles of H_2

The moles of H_2 = 0.0505 moles

The mass of H_2 = Moles of H_2 × Molar mass of H_2 = 0.0505 moles × 2.0158 g/mole = 0.10179 g

The mass of H_2 in the correct number of significant figures is 0.102 g.

Many laboratory gases are sold in steel cylinders with a volume of 43.8 L. What mass (in grams) of argon is inside a cylinder whose pressure is 17615kPa at 23∘C?

Answers

It's very simple... if we remember value of Universal Gas Constant R and Ideal Gas Law, so...

Ideal Gas Law
pV = nRT, where:
p - pressure (in kPa),
V - volume (in L),
n - number of moles (in mol),
R - universal cas constant (in kPa * L / mo l* K),
T - temperature (in K)

n = m/M, where:
n - number of moles,
m - mass (in grams),
M - molar mass of ingredient (in g/mol) - you find this at Periodic Table.

pV = nRT ---> pV = mRT/M ---> pVM = mRT ---> pVM/RT = m

p = 17615 kPa
T = 273.15 + 23 = 296.15 K
V = 43.8 L
R = 8.314 kPa * L / mol * K
M (for argon) = 39.948 g/mol

and

m = (17615 kPa * 48.3 L * 39.948 g/mol) / (296.15 K * 8.314 kPa * L / mol * K)
m = 13803.93 grams of Argon

What are two examples of an endothermic reaction and what are two examples of an ectothermic reaction?

Answers

Exothermic processes: Making ice cubes,formation of snow in clouds


Endothermic processe: Melting ice cubes, evaporation of water

When writing an electron configuration for a transition metal, what is the last orbital type to be filled – an s, p, d or f orbital?

Answers

It would be d.

Reason being said...

the electron configuration normally goes like this...

1s2 2s2 2p6 3s2 3p6 4s2....

until you hit the transition metals..remember those have a special rule..

even though you are in the 4 sublevels for the orbitals ... it goes down 1

Making it 3d..(1,2,3,4,5,6,7,8,9,10)

Going on...

at 5s2 then, 4d1, 4d2, 4d3, 4d4, etc..

at 6s2 then, 5d1, 6d2, 6d3, 6d4, etc..

Thus, D orbital is your answer.

Why can molten solution of ionic compounds be electrolysed

Answers

Answer:

the current is carried through the electrolyte by the movement of ions - not electrons.

Explanation:

The reason that an electrolyte has to be molten or in solution is that the current is carried through the electrolyte by the movement of ions - not electrons. In a solid, those ions can't move. It also follows, of course, that an electrolyte must contain ions.
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