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3 years ago

50 POINTS!!!!!!!!!!!

Chemistry

2 answers:

Pani-rosa [81]3 years ago

6 0

Answer:

Explanation:

kifflom [539]3 years ago

5 0

A substitution is a mutation that exchanges one base for another. This can include a change in a single chemical letter. ex. changing a to g or in your case g to a. I believe the correct answer should be B.

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Give the ground-state electron configuration for silicon (SiSi) using noble-gas shorthand. Express your answer in condensed form

nydimaria [60]

Answer:

[Ne] 3s² 3p²

Explanation:

Silicon atoms have 14 electrons. The ground state electron configuration of ground state gaseous neutral silicon is 1s²2s²2p⁶3s²3p².

Using noble gas shorthand, the electronic configuration is reduced to;

[Ne] 3s² 3p². Ne s the nearest noble gas to silicon, Ne contains 8 electrons, this means there's still 4 more electrons to fill. The s orrbital can only hold 2, hence the reaing two is transferred to the p orbital.

5 0

3 years ago

Which symbol can be used to indicate the pressure at which a chemical reaction is carried out? 25 degrees Celsius over a right a

jolli1 [7]

Answer:

2 atm

Explanation:

Chemical reactions are carried out at a certain rate. Sometimes that rate is quite slow, so we want to speed things up, which is usually used by increasing temperature, increasing pressure or adding a catalyst (a substance that increases the rate without changing itself).

If this is the case, then, when writing a chemical equation, we state these special conditions over a right arrow.

Now let's look at the answers:

- 25°C is a value and unit of temperature

- ∆ is a symbol that denotes change

- 2 atm is a value and unit of pressure (atmosphere is old unit for pressure)

- Pt is a chemical symbol for platinum, an element often used as a catalyst.

So, the correct answer is C) 2 atm

7 0

3 years ago

Read 2 more answers

One mole of aluminum atoms has a mass of 27 grams. How many grams are in 9.0 moles of aluminum?

gizmo_the_mogwai [7]

27*9=243 if one mole is equal to 27 grams times that by 9

6 0

2 years ago

Suppose an ice cube weighing 36.0 g at a temperature of 10°C is placed in 360 g water at a temperature of 20°C. Calculate the te

Scilla [17]

Answer:

10.44 °C

Explanation:

When the thermal equilibrium is reached, both of the substances have the same final temperature (T). The liquid water will lose heat, and the ice cube will absorb this heat. The temperature of the ice will increase until it reaches 0°C, at this temperature, it will change of phase for liquid, absorbing heat, but without a change in the temperature. Then the temperature will increase until the equilibrium.

By the energy conservation, the total amount of heat must be equal to 0:

Qice + Qmelting + Qliquid1 + Qliquid2 = 0

Liquid 1 is the ice after melting, and liquid 2 the liquid that was already at the flask. When there's a change of temperature:

Q = n*c*ΔT, where n is the number of moles, c is the heat capacity and ΔT is the temperature change (final - initial). The temperature variation in °C is equal in K, so the temperature may be used in °C.

The melting heat is:

Q = n*Hfus, Hfus = 6007 J/mol

The molar mass of the water is 18 g/mol, so the number of moles of the water and the ice are:

nwater = nliquid1 = 360/18 = 20 moles

nice = 36/18 = 2 moles

Qice + Qmelting + Qliquid1 + Qliquid2 = 0

2*38*(0 - (-10)) + 2*6007 + 2*75*(T - 0) + 20*75*(T - 20) = 0

760 + 12014 + 150T + 1500T - 30000 = 0

1650T = 17226

T = 10.44 °C

4 0

3 years ago

Which of the following are true statements about equilibrium systems? For the following reaction at equilibrium: CaCO3(s) ⇌ CaO(

Grace [21]

Answer:

The first, third and fourth statements are correct.

Explanation:

1) For the following reaction at equilibrium: CaCO3(s) ⇌ CaO(s) + CO2(g) adding more CaCO3 will shift the equilibrium to the right.

⇒ Le Chatellier says As the CaCO3 concentration is increased, the system will attempt to undo that concentration change by shifting the balance to the right. This statement is true.

2) For the following reaction at equilibrium: CaCO3(s)⇌ CaO(s) + CO2(g) increasing the total pressure by adding Ar(g) will shift the equilibrium to the right.

⇒ Le chatellier says that if we increase the pressure, the equilibrium will shift to the side with the least number of particles.

Since the molar densities of CaO and CaCO3 are constant, they don't appear in the equilibrium expression. This is why only changes to the pressure (concentration) of CO2 affect the position of the equilibrium.

If the pressure in the container is increased by adding an inert or non-reacting gas, nothing happens to the amounts of CO2, CaO or CaCO3. The added gas won't affect the partial pressure of CO2. This statement is false.

3)For the following reaction at equilibrium: 2 H2(g) + O2(g) ⇌ 2 H2O(g) the equilibrium will shift to the left if the volume is doubled.

⇒ Le Chatellier says if we increase the pressure, the equilibrium will shift to the side with the most particles.

In this case we have 2 moles of H2 and 1 mole of O2 on the left side and 2 mole of H2O on the right side. This means on the left side are more particles. So the equilibrium will shift to the left, so this statement is true.

4) For the following reaction at equilibrium: H2(g) + F2(g) ⇌ 2HF(g) removing H2 will increase the amount of F2 present once equilibrium is reestablished. Increasing the temperature of an endothermic reaction shifts the equilibrium position to the right.

⇒ Le chatellier says if H2 will be removed (this means the left side will get less particles) so the equilibrium will shift to the left, to increase the amount of F2.

⇒Le chatelier says if we increase the temperature of an exotherm reaction , there will be less energy released. The equilibrium will shift to the side of the reactants (the left side).

If we increase the temperature of an endotherm reaction, the equilibrium will shift to the side of the products (the right side). This statement is true.

4 0

3 years ago