Guest #4232

2 months ago

Hydrogen bonds.

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Question

Which of the two substances would have the higher boiling point ch4 or c?

Solution 1

Carbon has a higher boiling point.

Question

Which pair of elements do you expect to be most similar in their chemical properties?which pair of elements do you expect to be most similar in their chemical properties?ne and no and sibr and ik and fe?

Solution 1

Elements with the same properties would be in the same group (Up and down row). Look at a periodic table and see which of the elements are in the same group. That will be your answer.

Question

Question 1 a sample of 0.255 mole of gas has a volume of 748 ml at 28°c. calculate the pressure of this gas. (r= 0.0821 l ∙ atm / mol ∙ k) 0.784 atm 8.42 atm 0.00842 atm 7.84 × 10-4 atm none of the above

Solution 1

**Answer : The pressure of the gas is, 8.42 atm**

**Explanation :**

**Using ideal gas equation, **

where,

P = pressure of the gas = ?

V = volume of the gas = 748 ml = 0.748 L

conversion used : (1 L = 1000 ml)

T = temperature of the gas =

n = number of moles of the gas = 0.255 mole

R = gas constant = 0.0821 L.atm/mole.K

Now put all the given values in the ideal gas equation, we get the pressure of the gas.

**Therefore, the pressure of the gas is, 8.42 atm**

Solution 2

The correct answer to this complex question is 8.428 atm.

Question

Write a balanced nuclear equation for the beta decay of thallium-210.

Solution 1

210 0 206

Tl⇒ + Pb

81 -1 82

Tl⇒ + Pb

81 -1 82

Question

Write the balanced nuclear equation for β− decay of sodium−26. include both the mass numbers and the atomic numbers with each nuclear symbol. use the sup-subscript button in the answer palette to enter these numbers correctly. greek letters can be accessed in the drop-down menu that says -select−.

Solution 1

Β- decay is the emission of an electron by converting a neutron into a proton.

After doing β- decay, the formed daughter nucleus has the same number of mass number as the parent atom but the atomic number has increased by 1 and neutron number has reduced by 1.

If Na²⁶₁₁ (number of neutrons = 26 - 11 = 15) undergoes a β- decay, then produced daughter atom must have 12 protons and 14 neutrons. Hence, the daughter atom should be Mg.

**Na²⁶₁₁ → Mg²⁶₁₂ + ₋₁⁰β + energy**

After doing β- decay, the formed daughter nucleus has the same number of mass number as the parent atom but the atomic number has increased by 1 and neutron number has reduced by 1.

If Na²⁶₁₁ (number of neutrons = 26 - 11 = 15) undergoes a β- decay, then produced daughter atom must have 12 protons and 14 neutrons. Hence, the daughter atom should be Mg.

Solution 2

The **balanced nuclear equation** for **beta decay** of **sodium-26 **is represented as **Na²⁶₁₁ → Mg²⁶₁₂ + β₋₁⁰ + energy.**

**Beta decay** is one of the type of **radioactive nuclear decay** reaction in which **emission **of a** beta particle** takes place from the **atomic nuclear**.

**Beta particle** define by the symbol **β₋₁⁰** i.e. this particles has no **mass **but having a negative **charge **on it. In this reaction** atomic mass **of the **parent atom** is equal to the new formed **daughter atom**. But in this reaction** number** of **neutron **is reduced by 1 and number of proton is increased by one of parent atom. So, **balanced nuclear equation** for **β− decay **of **sodium−26** is represnted as:

**Na²⁶₁₁ → Mg²⁶₁₂ + β₋₁⁰ + energy**

Hence balanced **nuclear equation **for the **beta decay** is represented above.

To know more about **beta decay**, visit the below link:

Question

Write a short explanation about the “cheater” way to find the # of valence electrons an element has, and explain what valence electrons have to do with elements bonding?

Solution 1

I don’t know what the “cheater” way is, however you can easily judge how many valence electrons an element has by looking at its group number on the periodic table.

Bonding in chemistry is completely and totally due to electrons. Every element wants 8 electrons in its outer shell in order to be stable. This is what we call the “Octet Rule”.

Bonding in chemistry is completely and totally due to electrons. Every element wants 8 electrons in its outer shell in order to be stable. This is what we call the “Octet Rule”.

Question

¿A shaker of salt substitute contains 1.6 oz of K. What is the activity, in milliCuries, of the potassium in the shaker? The activity is 7 microcuries (µCi)

Solution 1

We know K-40 (potassium having atomic mass 40 g) is radioactive and its natural abundance is 0.012%

So for 1 mol of potassium contains 0.00012 mol of K-40

Now 1.6 oz of K = 45.36 g of K

average atomic weight of K = 39.1 g

so 45.36 g of K contains:

(45.36 / 39.1) * 0.00012 * 6.022 x 10²³ (atoms of K-40)

= 8.4 x 10¹⁹ atoms of K-40

We know, activity A is:

A = 0.693 / t1/2 N₀

[t1/2 : half life time and N₀ : initial number of atoms]

t1/2 of K-40 = 1.28 x 10⁹ years

= 4.04 x 10¹⁶ seconds

So A = (0.693 / 4.04 x 10¹⁶) * (8.4 x 10¹⁹ ) = 1441 cps

A = 141 x (1/3.7 x 10¹⁰) because 3.7 x 10¹⁰ cps = 1 Ci

A = 3.9 x 10⁻⁸ Ci = 3.9 x 10⁻⁵ millicurie

So for 1 mol of potassium contains 0.00012 mol of K-40

Now 1.6 oz of K = 45.36 g of K

average atomic weight of K = 39.1 g

so 45.36 g of K contains:

(45.36 / 39.1) * 0.00012 * 6.022 x 10²³ (atoms of K-40)

= 8.4 x 10¹⁹ atoms of K-40

We know, activity A is:

A = 0.693 / t1/2 N₀

[t1/2 : half life time and N₀ : initial number of atoms]

t1/2 of K-40 = 1.28 x 10⁹ years

= 4.04 x 10¹⁶ seconds

So A = (0.693 / 4.04 x 10¹⁶) * (8.4 x 10¹⁹ ) = 1441 cps

A = 141 x (1/3.7 x 10¹⁰) because 3.7 x 10¹⁰ cps = 1 Ci

A = 3.9 x 10⁻⁸ Ci = 3.9 x 10⁻⁵ millicurie

Question

A chemistry student mixes 5 grams of sodium chloride (NaCl) in 100 ml of water and stirs until all of the salt is dissolved. Once dissolved, the student measures the electrical conductivity of the solution. An additional 5 grams of NaCl is then dissolved in the solution. Which statement MOST accurately describes how the additional five grams of salt will affect the electrical conductivity of the solution?

Solution 1

When additional 5 grams of NaCl are dissolved in solution the **conductivity **of solution increases as more** ions **are available for conduction.

An** ion **is defined as an** atom** or a molecule which has a net electrical charge. There are **2 types** of ions :1) cation 2) anion . The** cation** is the positively charged ion and **anion **is the negatively charged ion . As they are oppositely charged they attract each resulting in the formation of ionic bond.

Ions consisting of single atom are mono-atomic ions while which consists of two or more ions are called as** poly-atomic ions **. They are created by chemical interactions . They are very reactive in their gaseous state and rapidly react with the oppositely charged ions resulting in** neutral molecules.**

Learn more about** ions**,here:

#SPJ2

Solution 2

I think the best choice is

A) The conductivity of the solution will increase because more ions are being added to the solution.

Because number ions will be increased, but big amount of NaCl can be still dissolved.

A) The conductivity of the solution will increase because more ions are being added to the solution.

Because number ions will be increased, but big amount of NaCl can be still dissolved.

Question

James is looking at a parallel circuit plan for lighting. There is a battery providing the power. There are switches labeled A,B,C,D that can be turned on to close the circuit. Which switch does not have to be on for light 3 to function?

Solution 1

The answer is D because for light 3 to function switch d does not have to turn on

Solution 2

For light 3 to function, switch D does not have to be on. This diagram shows a parallel circuit that provides more than one way for the current to return to the power source.

Question

Which of the following naturally orccuing radioisotopes would be most useful in dating objects

Solution 1

Potassium -40half life = 1.28 ×10∧9.

Radioisotope can be used to determine the age of fossils, to treat skin disease, to sterilize foodstuffs, and also to sterilize surgical instruments.

Radioisotope dating is a way to estimate a fossil's age by a method of analyzing the elemental isotopes which are within the rocks which it is in.

Radioisotope can be used to determine the age of fossils, to treat skin disease, to sterilize foodstuffs, and also to sterilize surgical instruments.

Radioisotope dating is a way to estimate a fossil's age by a method of analyzing the elemental isotopes which are within the rocks which it is in.

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