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3 years ago

what is the molecular formula of a compound with an empiricla formula of ch and a molecular mass of 78

Chemistry

1 answer:

Dovator [93]3 years ago

6 0

Answer:

C6H6

Explanation:

We can obtain the molecular formula from the empirical formula.

What we need do here is:

(CH)n = 78

The n shows the multiples of both element present in the actual compound. It can be seen that carbon and hydrogen have the same element ratio here. We then use the atomic masses of both elements to get the value of n. The atomic mass of carbon is 12 a.m.u while the atomic mass of hydrogen is 1 a.m.u

(1 + 12)n = 78

13n = 78

n = 78/13 = 6

The molecular formula is

(CH)n = (CH)6 = C6H6

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11.

Lostsunrise [7]

Answer:

(1) -12 Kcal/mol

Explanation:

Our answer options for this question are:

(1) -12 Kcal/mol

(2) -13 Kcal/mol

(3) -15 Kcal/mol

(4) -16 Kcal/mol

With this in mind, we can start with the chemical reaction (Figure 1). In this reaction, two bonds are broken, a C-H and a Br-Br. Additionally, a C-Br and a H-Br are formed.

If we want to calculate the enthalpy value, we can use the equation:

ΔH=ΔHbonds broken-ΔHbonds formed

If we use the energy values reported, its possible to calculate the energy for each set of bonds:

ΔHbonds broken

C-H = 94.5 Kcal/mol

Br-Br = 51.5 Kcal/mol

Therefore:

105 Kcal/mol + 53.5 Kcal/mol = 146 Kcal/mol

ΔHbonds formed

C-Br = 70.5 Kcal/mol

H-Br = 87.5 Kcal/mol

Therefore:

70.5 Kcal/mol + 87.5 Kcal/mol = 158 Kcal/mol

ΔH of reaction

ΔH=ΔHbonds broken-ΔHbonds formed=(146-158) Kcal/mol = -12 Kcal/mol

I hope it helps!

6 0

3 years ago

Discuss whether two products are required for a chemical reaction. (NEED HELP ASAP)

Alex787 [66]

Answer:

Yes.

Explanation:

"These starting substances of a chemical reaction are called the reactants, and the new substances that result are called the products."

There is a beginning product, and a reactant is needed in order for something to happen.

For example, according to Newton, something cannot happen until an exterior force comes and stops/pushes it.

Sorry if this is incorrect, I am just 4th grade :(

6 0

2 years ago

6) (a) Calculate the absorbance of the solution if its concentration is 0.0278 M and its molar extinction coefficient is 35.9 L/

Anvisha [2.4K]

Answer:

6) (a) 0.499; (b) 31.7 %

7) 0.15

Explanation:

6) (a) Absorbance

Beer's Law is

$A = \epsilon cl\\A = \text{35.9 L&\cdot$mol$^{-1}$cm$^{-1}$} $\times$ 0.0278 mol$\cdot$L$^{-1} \times $ 0.5 cm = \mathbf{0.499}$

(b) Percent transmission

$A = \log {\left (\dfrac{1}{T}}\right)}\\\\\%T = 100T\\\\T = \dfrac{\%T}{100}\\\\\dfrac{1}{T} = \dfrac{100 }{\%T}\\\\A = \log \left(\dfrac{100 }{\%T} \right ) = 2 - \log \%T\\\\0.499 = 2 - \log \%T\\\\\log \%T = 2 - 0.499 = 1.501\\\\\%T = 10^{1.501} = \mathbf{31.7}$

7) Absorbance

$A = \log \left (\dfrac{I_{0}}{I} \right ) = \log \left (\dfrac{I_{0}}{0.70I_{0}} \right ) = \log \left (\dfrac{1}{0.70} \right ) = -\log(0.70) = \mathbf{0.15}}$