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bekas [8.4K]
2 years ago
15

Help me out hear i need help

Chemistry
1 answer:
____ [38]2 years ago
6 0

Answer:

Explanation:

i cant see the attachment

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What is formed when 2 or more atoms are held together by covalent bonds?
Ksenya-84 [330]

The group of atoms held together by covalent bonds is called a molecule

7 0
3 years ago
If the half-life of a radioactive element is 4 days, how long will it take for three- fourths of a sample of the element to deca
Jlenok [28]

Answer:

\boxed{\text{8 da}}

Explanation:

The question will be easier to solve if we interpret it as, " How long will it take until one-fourth of a sample of the element remains,?"

The half-life of the element is the time it takes for half of it to decay.  

After one half-life, half (50 %) of the original amount will remain.  

After a second half-life, half of that amount (25 %) will remain, and so on.  

We can construct a table as follows:

\begin{array}{cccl}\textbf{No. of} & & \textbf{Fraction} & \\\textbf{half-lives} & \textbf{t/da} & \textbf{remaining} & \\1 & 4 & \dfrac{1}{2} & \\\\2 & 8 & \dfrac{1}{4}& \\\\3 & 12 & \dfrac{1}{8}& \\\end{array}

\text{We see that 8 da is two half-lives, and the fraction of the element remaining is $\frac{1}{4}$.}\\\text{It takes $\boxed{\textbf{8 da}}$ for three-fourths of the element to decay}

3 0
3 years ago
Identify the group of elements that corresponds to each of the following generalized electron configurations and indicate the nu
Alja [10]

Answer:

(a) [Noble gas] ns² np⁵: Number of unpaired electron is 1 and belongs to group 17 i.e. halogen group of the periodic table.

(b) [noble gas] ns² (n-1)d²: Number of unpaired electron is 2 and belongs to group 4 of the periodic table.

(c) [noble gas] ns² (n-1)d¹⁰ np¹: Number of unpaired electron is 1 and belongs to group 13 of the periodic table.

(d)[noble gas] ns² (n-2)f⁶ : Number of unpaired electron is 6 and belongs to group 8 of the periodic table.

Explanation:

In the Periodic table, the chemical elements are arranged in 7 rows, called periods and 18 columns, called groups. They are organized in increasing order of atomic numbers.

(a) [Noble gas] ns² np⁵

As the total number of electrons in the p-orbital is 5. Therefore, the number of unpaired electron is 1.

This element has 2 electrons in ns orbital and 5 electrons in np orbital. <u>So there are 7 valence electrons.</u>

Therefore, this element belongs to the group 17 i.e. halogen group of the periodic table.

(b) [noble gas] ns² (n-1)d²

As the total number of electrons in the d-orbital is 2. Therefore, the number of unpaired electrons is 2.

This element has 2 electrons in ns orbital and 2 electrons in (n-1)d orbital. So there are <u>4 valence electrons.</u>

Therefore, this element belongs to the group 4 of the periodic table.

(c) [noble gas] ns² (n-1)d¹⁰ np¹

As the total number of electrons in the p-orbital is 1. Therefore, the number of unpaired electron is 1.

This element has 2 electrons in ns orbital and 1 electron in np orbital. So there are <u>3 valence electrons</u>.

Therefore, this element belongs to the group 13 of the periodic table.

(d)[noble gas] ns² (n-2)f⁶

As the total number of electrons in the f-orbital is 6. Therefore, the number of unpaired electron is 6.

This element has 2 electrons in ns orbital and 6 electrons in (n-2)f orbital. So there are <u>8 valence electrons.</u>

Therefore, this element belongs to the group 8 of the periodic table.

3 0
2 years ago
During a reaction 24 cubic cm of carbon dioxide was given off. After 8 minutes no more gas was produced and the reaction was com
yuradex [85]

Answer:

Explanation:

Given parameters:

Volume of CO₂ = 24cm³

time taken for the reaction to complete = 8minutes.

Unknown:

rate of reaction

Soution

The reaction rate is a measure of speed of a chemical reaction. It is often calculated using the expression below:

    Reaction rate = \frac{change in concentration of reactant/product}{time taken}

   Reaction rate = \frac{24}{8} = 3cm³/min

In this reaction, 3cm³ of carbon dioxide were produced per minute

7 0
2 years ago
Read 2 more answers
A sample of nitrogen gas is stored in a 489.6 mL flask at 108 kPa and 10.0°C. The gas is transferred to a 750.0 mL flask at 28.7
Wewaii [24]

Answer:

P2= 125.26 Kpa

Explanation:

V1= 489.6 ml=0.4896L

V2= 750 ml= 0.750L

V1= 180 KPa= 180000 Pa

P2= ?

T1= 10 = 10 + 273.15 = 283.15K

T2= 28.7+273.15= 301.85K

180000Pa* 0.4896L/ 283.15K * 301.85K/0.75L

P2= 12526.28553

P2= 125.26 KPa

5 0
3 years ago
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