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3 years ago

Which numerical setup can be used to determine the atomic mass of lithium

Chemistry

2 answers:

irakobra [83]3 years ago

6 0

Answer:

Atomic mass of lithium is 7

Explanation:

Atomic mass is the mass of an atom and it is determined by the nucleus of an atom because the mass of electrons are very negligible.

Numerically, the mass of an atom = atomic number + number of neutrons

Atomic number is the total number of protons present in the nucleus of an atom.

Hence, atomic mass of lithium is

3 + 4 = 7

where 3 is the atomic number of lithium and 4 is the number of neutrons in lithium

denis-greek [22]3 years ago

3 0

Atomic Mass- Number of protons (Atomic number) + number of neutrons.
Hope this helps :)

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A solution that contains 3 grams of solute dissolved in 100 millimeters of solution is:

xxTIMURxx [149]

Answer:

the answer is correct part another is a part

Explanation:

c part

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2 years ago

A distance-time graph indicates that an object travels 2 m in 2 s and then travels another 30 m during the next 40 s.

Doss [256]

Answer:

$\boxed{\text{0.76m/s}}$

Explanation:

$\text{Average speed} = \dfrac{\text{total distance}}{\text{total time}}$

Total distance = 2 m + 30 m = 32 m

Total time = 2 s + 40 s = 42 s

$\text{Average speed} = \dfrac{\text{32 m}}{\text{42 s}} = \textbf{0.76 m/s}\\\text{The average speed of the object is $\boxed{\textbf{0.76m/s}}$}$

5 0

4 years ago

Describe the number of signals and their splitting in the 1H NMR spectrum of (CH3)2CHOCH3.

yanalaym [24]

Answer:

d. 3 signals: a singlet, a doublet, and a septet

Explanation:

In this case, we can start with the structure of $(CH_3)_2CHOCH_3$ . When we draw the molecule we will obtain 2-methoxypropane (see figure 1).

In 2-methoxypropane we will have three signals. The signal for the $CH_3$ groups in the left, the $CH$ and the $CH_3$ in the right. Lets analyse each one:

-) $CH_3$ in the right

In this carbon, we dont have any hydrogen as neighbors. Therfore we will have singlet signal in this carbon.

-) $CH$

In this case, we have 6 hydrogen neighbors ( the two methyl groups in the left). So, if we follow the n + 1 rule (where n is the amount of hydrogen neighbors):

$multiplicity~=~n+1~=~6~+~1~=~7$

For this carbon we will have a septet.

-) $CH_3$ in the left

In this case we have only 1 hydrogen neighbor (the hydrogen in $CH$ ). So, if we use the n+1 rule we will have:

$multiplicity~=~n+1~=~1~+~1~=~2$

We will have a doublet

With all this in mind the answer would be:

d. 3 signals: a singlet, a doublet, and a septet 

See figure 2 to further explanations

4 0

3 years ago

Small quantites of hydrogen gas can be prepared in the laboratory by the addition of aqueous hydrochloric acid to metallic zinc.

ira [324]

Answer: The mass or zinc reacted is 0.624 grams.

Explanation:

We are given:

Total pressure = 1.032 atm

Vapor pressure of water = 32 torr = 0.042 atm (Conversion factor: 1 atm = 760 torr)

To calculate partial pressure of hydrogen gas, we use the equation:

$p_{H_2}=p_T-p_{H_2O}\\\\p_{H_2}=1.032-0.042=0.99atm$

To calculate the number of moles of hydrogen gas, we use the equation given by ideal gas follows:

$PV=nRT$

where,

P = pressure of hydrogen gas = 0.99 atm

V = Volume of hydrogen gas = 240. mL = 0.240 L (Conversion factor: 1 L = 1000 mL)

T = Temperature of hydrogen gas = $30^oC=[30+273]K=303K$

R = Gas constant = $0.0821\text{ L. atm }mol^{-1}K^{-1}$

n = number of moles of hydrogen gas = ?

Putting values in above equation, we get:

$0.99atm\times 0.240L=n\times 0.0821\text{ L atm }mol^{-1}K^{-1}\times 303K\\n=\frac{0.99\times 0.240}{0.0821\times 303}=9.55\times 10^{-3}mol$

The chemical equation for the reaction of zinc and hydrochloric acid follows:

$Zn+2HCl\rightarrow ZnCl_2+H_2$

By Stoichiometry of the reaction:

1 mole of hydrogen gas is produced from 1 mole of zinc metal

So, $9.55\times 10^{-3}mol$ of hydrogen gas is produced from = $\frac{1}{1}\times 9.55\times 10^{-3}=9.55\times 10^{-3}mol$ of zinc metal

To calculate the mass of zinc metal, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Molar mass of zinc = 65.38 g/mol

Moles of zinc = $9.55\times 10^{-3}$ moles

Putting values in above equation, we get:

$9.55\times 10^{-3}mol=\frac{\text{Mass of zinc}}{65.38g/mol}\\\\\text{Mass of zinc}=(9.55\times 10^{-3}mol\times 65.38g/mol)=0.624g$

Hence, the mass or zinc reacted is 0.624 grams.

4 0

4 years ago

A chemistry student must write down in her lab notebook the concentration of a solution of potassium chloride. The concentration

DerKrebs [107]

Answer:

3.65 g / ml correct to 3 sig. fig.

Explanation:

The computation of the concentration required is shown below:

As we know that

[A] = mass of solute ÷ volume of solution

Before that first find the mass of solute

Given that

Initial weight = 5.55g

And,

Final weight = 92.7 g

So,

Mass of KCl is

= 92.7 - 5.55

= 87.15 g ~ 87.2 g

Now the KCi is fully dissolved, so the volume is 23.9 ml

So, concentration is

= 87.2 g ÷ 23.9 ml

= 3.65 g / ml correct to 3 sig. fig.

6 0

3 years ago