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Tamiku [17]
3 years ago
9

I WILL GIVE BRAINLIEST. When a mole of lithium reacts chemically with hydrogen to form lithium hydride, the energy released is f

ound to be roughly 90 joules. How much mass is lost?
1.0 x 10-15 kg
2.7 x 1010 kg
1.0 x 1015 kg
3.0 x 10-7 kg
Chemistry
2 answers:
leva [86]3 years ago
8 0

Answer : The mass lost is, 1.0\times 10^{-15}Kg

Explanation :

According to the Einstein equation, the energy is equal to the product of mass and the square of the speed of light.

The mathematical expression is :

E=m\times c^2

where,

E = energy  = 90 J = 90Kg.m^2/s^2

c = speed of light = 3\times 10^8m/s

m = mass = ?

Now put all the given values in the above formula, we get the amount of energy released.

90Kg.m^2/s^2=m\times (3\times 10^8m/s)^2

m=1.0\times 10^{-15}Kg

Therefore, the mass lost is, 1.0\times 10^{-15}Kg

Softa [21]3 years ago
4 0
The answer is 3.0 * 10^-7
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PIT_PIT [208]

The question is incomplete, complete question is :

Determine the pH of an HF solution of each of the following concentrations. In which cases can you not make the simplifying assumption that x is small? (K_a for HF is 6.8\times 10^{-4}.)

[HF] = 0.280 M

Express your answer to two decimal places.

Answer:

The pH of an 0.280 M HF solution is 1.87.

Explanation:3

Initial concentration if HF = c = 0.280 M

Dissociation constant of the HF = K_a=6.8\times 10^{-4}

HF\rightleftharpoons H^++F^-

Initially

c          0            0

At equilibrium :

(c-x)      x             x

The expression of disassociation constant is given as:

K_a=\frac{[H^+][F^-]}{[HF]}

K_a=\frac{x\times x}{(c-x)}

6.8\times 10^{-4}=\frac{x^2}{(0.280 M-x)}

Solving for x, we get:

x = 0.01346 M

So, the concentration of hydrogen ion at equilibrium is :

[H^+]=x=0.01346 M

The pH of the solution is ;

pH=-\log[H^+]=-\log[0.01346 M]=1.87

The pH of an 0.280 M HF solution is 1.87.

6 0
3 years ago
A student sees an absorbance a=1.140 for his solution that has a concentration of c=1.50*10-4 m using 0.50 cm cuvette. what is t
777dan777 [17]

The molar extinction coefficient is 15,200 M^{-1} cm^{-1}.

The formula to be used to calculate molar extinction coefficient is -

A = ξcl, where A represents absorption, ξ refers molar extinction coefficient, c refers to concentration and l represents length.

The given values are in required units, hence, there is no need to convert them. Directly keeping the values in formula to find the value of molar extinction coefficient.

Rewriting the formula as per molar extinction coefficient -

ξ = \frac{A}{cl}

ξ = \frac{1.140}{1.5*10^{-4}*0.5 }

Performing multiplication in denominator to find the value of molar extinction coefficient

ξ = \frac{1.140}{0.000075}  

Performing division to find the value of molar extinction coefficient

ξ = 15,200 M^{-1} cm^{-1}

Hence, the molar extinction coefficient is  15,200 M^{-1} cm^{-1}.

Learn more about molar extinction coefficient -

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6 0
2 years ago
Can someone help me with this please
never [62]

Answer: B. 1:2

Explanation: Beryllium and chlorine forms a binary ionic compound. Ionic compound is formed when a metal loses its electrons to a receiving non metal. Beryllium (metal) has two valence electrons while chlorine (nonmetal) has seven valence electrons, and so a beryllium atom has to give out its two valence electrons to attain a duplet stable structure while a chlorine atom will gain one electron to attain its stable octet structure. In the reaction between beryllium and chlorine, two atoms of chlorine have to accept the two electrons from one beryllium atom to attain their stable octet structure.

The formula of the compound formed is BeCl2.

3 0
4 years ago
Calculate the mass (grams) of 0.750 moles of Al2(Cr2O7)3
garik1379 [7]

Answer:

526g is the mass of this sample

Explanation:

To solve this question we must, as first, find the <em>molar mass </em>of Al₂(Cr₂O₇)₃ using the periodic table. The molar mass is defined as the mass of this compound per mole. With this value we can find the mass in 0.750 moles as follows:

<em>Molar mass Al₂(Cr₂O₇)₃</em>

2Al = 2*26.98g/mol = 53.96g/mol

6 Cr = 6*51.9961g/mol = 311.9766g/mol

21 O = 21*15.999g/mol = 335.979g/mol

53.96g/mol + 311.9766g/mol + 335.979g/mol

= 701.9156g/mol

The mass of 0.750 moles is:

0.750 moles * (701.9156g / mol) =

<h3>526g is the mass of this sample</h3>
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Answer:

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The element Sm describe is called Samarium. This element has unique sets of properties that makes it very unique and distinct.

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