What is the bright band we call the Milky Way?

What are the advantages and disadvantages of using an egg to model organelles in an animal c of using an egg to model organelles

aleksandrvk [35]

I think its because an egg doesnt have the right chemical make up

7 0

3 years ago

Can someone help me? It needs to have a diagram that has arrows.

daser333 [38]

Answer: The enthalpy change for formation of butane is -125 kJ/mol

Explanation:

The balanced chemical reaction is,

$C_4H_{10}(g)+\frac{13}{2}O_2(g)\rightarrow 4CO_2(g)+5H_2O(l)$

The expression for enthalpy change is,

$\Delta H=[n\times H_f{products}]-[n\times H_f{reactants}]$

Putting the values we get :

$\Delta H=[4\times H_f_{CO_2}+5\times H_f_{H_2O}]-[1\times H_f_{C_4H_{10}}+\frac{13}{2}\times H_f_{O_2}]$

$-2877=[(4\times -393)+(5\times -286)]-[1\times H_f_{C_4H_{10}}+\frac{13}{2}\times 0]$

$H_f_{C_4H_{10}=-125kJ/mol$

Thus enthalpy change for formation of butane is -125 kJ/mol

5 0

3 years ago

Calculate molality,molarity and mole fraction of KI if the density of 20%(mass) aqueous KI is 1.202 g/mL

Scorpion4ik [409]

Basis: 1 L of the substance.
(1.202 g/mL) x (1000 mL) = 1202 g
mass solute = (1202 g) x 0.2 = 240.2 g
mass solvent = 1202 g x 0.8 = 961.6 g
moles KI = (240.2 g) x (1 mole / 166 g) = 1.45 moles
moles water = (961.6 g) x (1 mole / 18 g) = 53.42 moles
1. Molality = moles solute / kg solvent
= 1.45 moles / 0.9616 kg = 1.5 m
2. Molarity = moles solute / L solution
= 1.45 moles / 1 L solution = 1.45 M
3. molar mass = mole solute / total moles
= 1.45 moles / (1.45 moles + 53.42 moles) = 0.0264

5 0

3 years ago

What is the molecular formula for C3H2N?

NNADVOKAT [17]

It is empirical formula

5 0

3 years ago

Read 2 more answers

PLEASE ANSWER Which is/are true?

Alona [7]

You have to check each statement, so this is equivalent to 5 different questions.

Answers:

The true statements are:

b. Si has valence electrons in the n = 3 energy level.

d. Xe has valence electrons in the n = 5 energy level.

Explanations:

a. Li has valence electrons in the n = 1 energy level.

Answer: False.

Valence electrons are the electrons in the outermost main energy level (shell of electrons).

To determine where the valence electrons are, you build the electron configuration, using Aufbau rules to predict the orbital filling: in increasing order of energy.

The atomic number of lithium (Li) is 3. Hence, you have to distribute 3 electrons, and so its electron confiuration is:

1s² 2s¹

The only valence electron is in the 2s orbital, i.e. in the n = 2 energy level.

b. Si has valence electrons in the n = 3 energy level.

Answer: True

Silicon (Si) has atomic number 14, so you have to distribute 14 electrons in increasing order of energy:

1s² 2s² 2p⁶ 3s² 3p²

Thus, Si has five valence electrons, and they are in the n = 3 energy level.

c. Ga has valence electrons in the n = 3 energy level.

Answer: False

Gallium has atomic number 31, so you have to distribute 31 electrons, filling the orbitals in increasing order of enery.

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p¹

The highest energy level is 4. This is where the valence electrons are. So, Ga has the valence electrons in the n = 4 level (not n = 3 as the statement describes).

d. Xe has valence electrons in the n = 5 energy level.

Answer: True

The atomic number of Xe is 54.

Using the short notation (noble gas notation), and filling the orbitals in increasing order of energy, you get the configuration:

[Kr] 5s² 4d¹⁰ 5p⁶.

Hence, the valence electrons are in the n ) 5 level, such as the statement describes.

e. P has valence electrons in the n = 2 energy level.

Answer: False

Phosphorus (P) has atomic number 15, hence there are 15 electrons.

The electron configuration following the increasing order of energy, which you can remember using Aufbau rules, is:

1s² 2s² 3s² 3p³

Then, the valence electrons are in the n = 3 energy level; not in the n = 2 energy level.

3 0

3 years ago