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1 year ago

Which reaction can be used to calculate the enthalpy of formation of a substance

Chemistry

1 answer:

Zielflug [23.3K]1 year ago

4 0

ANSWER

option B

EXPLANATION

Firstly, we will need to define the standard heat of formation

The standard heat of formation is the amount of heat evolved or absorbed when one mole of a compound is completely formed from its constituent elements under standard conditions.

From the options provided, you will see that only option B aligns with the definition of the standard heat of formation.

$\text{ H}_{2(g)}+\text{ }\frac{1}{2}O_2\rightarrow\text{ H}_2O(l)$

From the above reaction, you will see that 1 mole of water is formed from hydrogen and oxygen.

Hence, the answer is option B

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PLLLLEEAASEEE HELLPP!!

nekit [7.7K]

<u>Answer:</u> The correct option is C) 1.68 mol/L

<u>Explanation:</u>

Molarity is defined as the amount of solute expressed in the number of moles present per liter of solution. The units of molarity are mol/L. The formula used to calculate molarity:

$\text{Molarity of solution}=\frac{\text{Given mass of solute}}{\text{Molar mass of solute}\times \text{Volume of solution (L)}}$ .....(1)

Given values:

Given mass of $C_6H_{12}O_6$ = 150 g

Molar mass of $C_6H_{12}O_6$ = 180 g/mol

Volume of the solution = 0.50 L

Putting values in equation 1, we get:

$\text{Molarity of solution}=\frac{150}{180\times 0.50}\\\\\text{Molarity of solution}=1.68M$

Hence, the correct option is C) 1.68 mol/L

7 0

3 years ago

Find the mass, in grams, of 5.00*10^23 molecules of F2

Westkost [7]

Answer: 31.55 g

Explanation:

- The mass number of Fluoride atom (F) = 18.99 g/mol, so mass number of fluorine gas (F2) = 37.98 g/mol.

- 1 mole of (F2) [which has 37.98 g/mol] contains Avogadro’s number of molecules (6.02×10^23 molecules),

so 1 mole of (F2) with 37.98 g/mol → 6.02×10^23 molecules.

- Using cross multiplication,

37.98 g/mol of (F2) → 6.02 ×10^23 molecules

? → 5.00 ×10^23 molecules

Hence the mass of 5.00×10^23 molecules of F2 = (37.98 × 5.00 × 10^23) / 6.02 ×10^23 = 31.55 g..

7 0

4 years ago

Which of the following is an example of pseudo science

Otrada [13]

Answer:

Astrology

Explanation:

One characteristic of science is that it must be reproducible. Other scientists must be able to repeat the original experiments and get the same result. That's what makes scientific claims reliable.

Astrology contends that the positions and motions of stars and planets can affect people and events on Earth. This has been disproved, so astrology is a pseudoscience .

Biology, chemistry, and physics are sciences.

7 0

4 years ago

Rocks crack and shift when ? from moving plates become to great

Ann [662]

Pressure Plates there is different types of plates also

5 0

4 years ago

Radioactive carbon-14 has a half life of 5730 years. Suppose a peice of wood has a decay rate of 15 disintegrations per minute.

Tom [10]

Answer:

$\large \boxed{\text{2920 yr}}$

Explanation:

Two important formulas in radioactive decay are

$(1) \qquad t_{\frac{1}{2}} = \dfrac{\ln 2}{k}\\\\(2) \qquad \ln \left(\dfrac{N_{0}}{N}\right) = kt$

1. Calculate the decay constant k

$\begin{array}{rcl}t_{\frac{1}{2}} &=& \dfrac{\ln 2}{k}\\\\\text{1530 yr} &= &\dfrac{\ln 2}{k}\\\\k & = & \dfrac{\ln 2}{\text{1530 yr}}\\\\& = & 4.530 \times 10^{-4} \text{ yr}^{-1}\\\end{array}$

2. Calculate the time

$\begin{array}{rcl}\ln \left(\dfrac{N_{0}}{N}\right) &= &kt \\\\\ln \left(\dfrac{15}{4}\right) &= &4.530 \times 10^{-4} \text{ yr}^{-1}\times t \\\\\ln 3.75 &= &4.530 \times 10^{-4} \text{ yr}^{-1}\times t \\t &= &\dfrac{\ln 3.75}{4.530 \times 10^{-4} \text{ yr}^{-1}}\\\\& = & \textbf{2920 yr}\\\end{array}\\\text{It would take $\large \boxed{\textbf{2920 yr}}$ for the rate to decrease to 4 dis/min.}$

5 0

4 years ago