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2 years ago

Which phrase describes valence electrons? (1 point)

Chemistry

2 answers:

dimaraw [331]2 years ago

7 0

Answer:

the electrons in an atom's outermost energy level

Explanation:

Anna11 [10]2 years ago

4 0

Answer:

Explanation:

the electrons in an atom's outermost energy level

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A wooden tool is found at an archaeological site. Estimate the age of the tool using the following information: A 100 gram sampl

lord [1]

Answer:

2578.99 years

Explanation:

Given that:

100 g of the wood is emitting 1120 β-particles per minute

Also,

1 g of the wood is emitting 11.20 β-particles per minute

Given, Decay rate = 15.3 % per minute per gram

So,

Concentration left can be calculated as:-

C left = $[A_t]=\frac{11.20\ per\ minute}{15.3\ per\ minute\ per\ gram}\times [A_0]= 0.7320[A_0]$

Where,

$[A_t]$ is the concentration at time t

$[A_0]$ is the initial concentration

Also, Half life of carbon-14 = 5730 years

$t_{1/2}=\frac {ln\ 2}{k}$

Where, k is rate constant

So,

$k=\frac {ln\ 2}{t_{1/2}}$

$k=\frac {ln\ 2}{5730}\ years^{-1}$

The rate constant, k = 0.000120968 year⁻¹

Time =?

Using integrated rate law for first order kinetics as:

$[A_t]=[A_0]e^{-kt}$

So,

$\frac {[A_t]}{[A_0]}=e^{-0.000120968\times t}$

$\frac {0.7320[A_0]}{[A_0]}=e^{-0.000120968\times t}$

$0.7320=e^{-0.000120968\times t}$

$ln\ 0.7320=-0.000120968\times t$

<u>t = 2578.99 years</u>

8 0

3 years ago

What is the correct 1 letter code for the amino acid sequence Glutamic Acid-Histadine-Tyrosine Select one: a. E-H-Y b. G-H-T c.

EastWind [94]

Answer:

a. E-H-Y

Explanation:

A group of three nucleotides is called a codon that codes for a specific amino acid in the protein. There are 20 essential amino acids present in human body and are required in the diet.

Each amino acid is given a one-letter code that makes the study of amino acid sequences easy. One letter code for the given amino acid sequence Glutamic Acid-Histidine-Tyrosine is E-H-Y in which E is code for Glutamic Acid, H is a code for Histidine, and Y is a code for Tyrosine.

Hence, the correct answer is "a. E-H-Y".

6 0

3 years ago

A chemical reaction takes place in which energy is absorbed. Arrange the characteristics of the reaction in order from start to

marshall27 [118]

Endothermic reactions, on the other hand, absorb heat and/or light from their surroundings. For example, decomposition reactions are usually endothermic. In endothermic reactions, the products have more enthalpy than the reactants. Thus, an endothermic reaction is said to have a positive<span> enthalpy of reaction. This means that the energy required to break the bonds in the reactants is more than the energy released when new bonds form in the products; in other words, the reaction requires energy to proceed.</span>

3 0

3 years ago

Read 2 more answers

We can also use the activity series to predict reactions between a metal and an acid. what are the products of the reaction fe(s

andrew11 [14]

Answer;

FeSO4 (aq) + H2 (g)

Explanation;

The reaction between iron and dilute sulfuric acid gives a salt and hydrogen gas. (iron (ii) sulfate and hydrogen gas).

The equation for the reaction is;

Fe(s) + H2SO4 (aq) = FeSO4(aq) +H2(g)

8 0

3 years ago

What is possible mass number of a sodium atom, Na?

den301095 [7]

Answer:

The possible mass of the number of sodium is 23amu

3 0

2 years ago