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3 years ago

Which of these elements has an electron configuration of [Kr]5s2?

Chemistry

1 answer:

beks73 [17]3 years ago

5 0

Strontium has an electron configuration of [Kr]5s²

<h3>Further explanation </h3>

In an atom there are levels of energy in the shell and sub shell

This energy level is expressed in the form of electron configurations.

Writing electron configurations starts from the lowest to the highest sub-shell energy level. There are 4 sub-shells in the shell of an atom, namely s, p, d and f. The maximum number of electrons for each sub shell is

s: 2 electrons

p: 6 electrons

d: 10 electrons and

f: 14 electrons

From an electron configuration of [Kr]5s² can be concluded :

element is in period 5 (5 = shell)
element is group 2(valence electron =2 and block s)
has atomic number 38 (Kr = 36 + 2(valence elektron from 5s²)

If we look at the periodic system, the elements that meet the requirements in question are Strontium (Sr)

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If 4.70 L of CO2 gas at 22 ∘C at 789 mmHg is used, what is the final volume, in liters, of the gas at 37 ∘C and a pressure of 75

lutik1710 [3]

Answer:

Final Volume = 5.18 Liters

Explanation:

Initial Condition:

P1 = 789 mm Hg x (1/760) atm /mm Hg = 1.038 atm

T1 = 22° C = 273 + 22 = 295 K

V1 = 4.7 L

Final Condition:

P2 = 755 mm Hg x (1/760) atm /mm Hg = 0.99 atm

T2 = 37° C = 273 + 37 = 310 K

V2 = ?

Since, (P1 x V1) / T1 = (P2 x V2) / T2,

Therefore,

⇒ (1.038)(4.7) / 295 = (0.99)(V2) / 310

⇒ V2 = 5.18 L (Final Volume)

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2 years ago

Refer to the Chemical Compounds table above. How many total elements are in<br> Ethanol?

Korolek [52]

Answer:

3 element i.e carbon (C), hydrogen (H) and oxygen.

Explanation:

The following data were obtained from the question:

Subtance >>>>>>>> Chemical Formula

Glucose >>>>>>>>> C₆H₁₂O₆

Methane >>>>>>>> CH₄

Ethanol >>>>>>>>> C₂H₅OH

Hydrogen peroxide >> H₂O₂

From the above table, we can see that ethanol (C₂H₅OH) contains carbon (C), hydrogen (H) and oxygen

Therefore, the total number of elements present in ethanol, C₂H₅OH is 3.

8 0

3 years ago

Given: 4Na + O2 → 2Na2O In this chemical reaction, how many moles of Na2O will be produced if 2.90 moles of Na react completely?

crimeas [40]

Since we already have the balanced equation, we know that the ratio between $Na:Na_{2}O$ is $4:2$ respectively.

So then we can set up a proportion to find the number of moles produced when 2.90 moles of Na react completely:

$\frac{4mol_{Na}}{2mol_{Na_{2}O}} =\frac{2.90mol_{Na}}{xmol_{Na_{2}O}}$

Then we cross multiply and solve for x:

$4x=5.8$

$x=1.45$

Therefore, we know that when 2.90 moles of Na react completely, there are 1.45 moles of $Na_{2}O$ that are produced.

3 0

2 years ago

1. Which of the following is a correctly written thermochemical equation?

WITCHER [35]

Explanation:

1. Thermochemical equation is balance stoichiometric chemical equation written with the phases of the reactants and products in the brackets along with the enthalpy change of the reaction.

The given correct thermochemical reactions are:

$Fe(s)+O_2(g)\rightarrow Fe_2O_3(s),\Delta H = 3,926 kJ
$

$C_3H_8(g)+5O_2 (g)\rightarrow 3CO_2 (g)+4H_2O(l),\Delta H= 2,220 kJ/mol$

2. Phase change affect the value of the enthalpy change of the thermochemical equation. This is because change in phase is accompanied by change in energy. For example:

$H_2O(s)\rightarrow H_2O(g),\Delta H_{s}=51.1 kJ/mol$