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3 years ago

True or False: PERIODS on the periodic table run up and down.

Chemistry

2 answers:

olganol [36]3 years ago

6 0

Answer:

True

Explanation:

I guessed XD But I also used Google and that's what I got

Leviafan [203]3 years ago

3 0

The answer is true PERIODS on the periodic table run up and down

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The elements that contain electrons in an F sublevel near the highest occupied energy level are referred to as?

Mrac [35]

inner transmission levels i took the test

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3 years ago

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Covalent compounds occur------

irga5000 [103]

Answer:

Only between nonmetals

Explanation:

Covalent compounds are compounds that are formed as a result of covalent bonding between nonmetal atoms.
Covalent compounds occur only between non metals, where atoms of the nonmetals involved join to form a covalent bond as a result of sharing of electrons.
Electrons shared during the formation of covalent bond, may be from one atom involved or each atom contributing equally to the bond formation.
An example of covalent compounds include, phosphorus (v) oxide, methane, water, CO2,etc.

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3 years ago

Calculate the pH of 1.00 L of a buffer that contains 0.105 M HNO2 and 0.170 M NaNO2. What is the pH of the same buffer after the

kari74 [83]

Answer:

1.- pH =3.61

2.-pH =3.53

Explanation:

In the first part of this problem we can compute the pH of the buffer by making use of the Henderson-Hasselbach equation,

pH = pKa + log [A⁻]/[HA]

where [A⁻] is the conjugate base anion concentration ( [NO₂⁻]), [HA] is the weak acid concentration,[HNO₂].

In the second part, our strategy has to take into account that some of the weak base NO₂⁻ will be consumed by reaction with the very strong acid HCl. Thus, first we will calculate the new concentrations, and then find the new pH similar to the first part.

First Part

pH = 3.40+ log {0.170 /0.105}

pH = 3.61

Second Part

# mol HCl = ( 0.001 L ) x 12.0 mol / L = 0.012

# mol NaNO₂ reacted = 0.012 mol ( 1: 1 reaction)

# mol NaNO₂ initial = 0.170 mol/L x 1 L = 0.170 mol

# mol NaNO₂ remaining = (0.170 - 0.012) mol = 0.158

# mol HNO₂ produced = 0.012 mol

# mol HNO₂ initial = 0.105

# new mol HNO₂ = (0.105 + 0.012) mol = 0.117 mol

Now we are ready to use the Henderson-Hasselbach with the new ration. Notice that we dont have to calculate the concentration (M) since we are using a ratio.

pH = 3.40 + log {0.158/.0117}

pH = 3.53

Notice there is little variation in the pH of the buffer. That is the usefulness of buffers.

4 0

2 years ago

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Which of the following contains the same number of electrons as an atom of neon?

asambeis [7]

Answer:

D. $O^{2-}$

Explanation:

In Chemistry, electrons can be defined as subatomic particles that are negatively charged and as such has a magnitude of -1.

Valence electrons can be defined as the number of electrons present in the outermost shell of an atom. Valence electrons are used to determine whether an atom or group of elements found in a periodic table can bond with others. Thus, this property is typically used to determine the chemical properties of elements.

Oxygen has a total number of eight (8) electrons and as such the $O^{2-}$ is able to gain (receive) two (2) more electrons in order to have the same electron arrangements as the noble gas i.e an atom of neon that has a total number of ten (10) electrons.

Hence, $O^{2-}$ contains the same number of electrons as an atom of neon.

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2 years ago

Calcium carbide (CaC2) reacts with water to form acetylene (C2H2) and Ca(OH)2.

Sergio [31]

The answer is -60.57 = -60.6 KJ.
CaC2(s) + 2 H2O(l) ---> Ca(OH)2(s) +C2H2(g) H= -127.2 KJ
Hf C2H2 = 226.77
Hf Ca(OH)2 = -986.2
Hf H2O = -285.83
Now,

add them up. 226.77 - 986.2 + (2*285.83) = -187.77
Add back the total enthalpy that is given in the question
-187.77+127.2 = -60.57

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3 years ago

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