All categories

3 years ago

According to Hess’s law, if a series of intermediate reactions are combined, the enthalpy change of the overall reaction is

Chemistry

2 answers:

sdas [7]3 years ago

4 0

I think the answer is B. the sum of the enthalpy changes of the intermidiate reactions

kolezko [41]3 years ago

4 0

Answer : The correct option is, the sum of the enthalpy changes of the intermediate reactions.

Explanation :

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.

For example :

The formation reaction of CO will be,

$C(graphite)+\frac{1}{2}O_2(g)\rightarrow CO(g)$ $\Delta H_{formation}$

The intermediate balanced chemical reaction will be,

(1) $C(graphite)+\frac{1}{2}O_2(g)\rightarrow CO_2(g)$ $\Delta H_1$

(2) $CO+\frac{1}{2}O_2(g)\rightarrow CO_2(g)$ $\Delta H_2$

The expression for enthalpy of formation of CO is,

$\Delta H_{formation}=[n\times \Delta H_1]+[n\times \Delta H_2]$

where,

n = number of moles

By adding reaction 1 and reverse reaction of reaction 2, we get the enthalpy of formation of CO.

Hence, the correct option is, the sum of the enthalpy changes of the intermediate reactions.

You might be interested in

The air inside a hot-air balloon is heated to 59.00 °C (Tinitial) and then cools to 39.00 °C (Tfinal). By what percentage does t

Mama L [17]

Answer:

6.1%

Explanation:

Assuming pressure inside balloon remains constant during the temperature change.

Therefore, as per Charles' law at constant pressure,

$\frac{V_1}{T_1} =\frac{V_2}{T_2}$

$T_2=39\°\ C=39+273=312\ K$

$T_1=59°\ C=273+59=332\ K$

$V_2=V_1\times \frac{T_2}{T_1} \\=V_1\times\frac{312}{332}\\=0.939V_1$

Percentage change in volume

$\%\ change\ in\ volume=\frac{V_1-0.939V_1}{V_1} \times 100\\=6.1\%$

Change in volume of the balloon is 6.1%

4 0

3 years ago

Put the steps of the carbon cycle in order using Step 1 as your starting point. Step 1: Bacteria, through nitrogen fixation and

Amanda [17]

Answer:

The answer is explained below

Explanation:

Put the steps of the carbon cycle in order using Step 1 as your starting point

Step 1: Bacteria, through nitrogen fixation and nitrification, convert nitrogen into a usable form. The animal dies and decomposes, returning nitrogen back to the soil. Once nitrogen is in usable form, it is taken up by plants and assimilated into proteins.. An animal eats a plant and the nitrogen becomes part of the animal’s proteins.

The steps taking in the carbon circle using step 1 as the starting point is as follows:

Step 1: Bacteria, through nitrogen fixation and nitrification, convert nitrogen into a usable form.

Bacteria convert nitrogen into nitrites and nitrates through the process of nitrification. Nitrites and nitrates are in the form that can be used by the plants

Step 2: Once nitrogen is in usable form, it is taken up by plants and assimilated into proteins.

The Nitrogen can only be used by the plants when in nitrites and nitrates form. When in this form, it is then assimilated into plant tissue as protein.

Step 3: An animal eats a plant and the nitrogen becomes part of the animal’s proteins.

An animal such as rabbit eats the plant and the protein in the plant becomes protein in the animal.

Step 4: The animal dies and decomposes, returning nitrogen back to the soil.

When the animal dies, the animal undergoes decomposition and the nitrogen in the animal is returned to the soil

5 0

3 years ago

In the lab you measure a clean dry crucible and cover to be 24.36 grams. You obtain a 2cm piece of pure magnesium metal. After s

mart [117]

Answer:

1) 0.3g Mg

2)0.5g MgO

3)0.2g O

4)0.01mol Mg & 0.01mol O

5)0.01mol MgO

6) Empirical formula MgO

Explanation:

The mass og Mg is obtained by substracting 24.36g from 24.66g:

24.66 - 24.36 = 0.3g Mg

The ignition of Mg means that it's reacting with oxygen to form an oxide. The increase in the crucible mass after the Mg ignition is due to the addition of oxygen. However, the addition of few drops of water produces a new compound: a hydroxide. According to the oxidation state og Mg (2+), the only magnesium oxide possible is MgO. It happens because the oxidation state of oxygen in oxides is 2-. Which means that just one oxygen atom is required to electrically neutralize one magnesium atom.

We can use a conversion factor to know how much MgO is made from from 0.3 g of Mg:

$0.3g Mg$ * $\frac{16gO}{24.3gMg}$ = 0.2g O

Thereby the mass of the oxide is 0.2g O + 0.3g Mg = 0.5g MgO

We convert the mass of oxygen and magnesium to the respective amounts in moles by using conversion factors:

$0.2g O$ * $\frac{1 mol O}{16g O}$ = 0.01mol O

$0.3g Mg$ * $\frac{1mol Mg}{24.3g Mg}$ = 0.01mol Mg

The moles of MgO can be obtained from:

$0.5g MgO$ * $\frac{1mol MgO}{40.3g MgO}$ = 0.01mol MgO

To obtain the empirical formula, the amount fo moles of each elements must be divided by the smallest one, in this case, 0.01.

The result for both number of Mg atoms and O atoms is 1. This can be interpreted to mean that there is a Mg atom for each O atom forming the formula unit of the compound.

The step when water is added to the compound resulting after heating does not affect the calculations necessary for the magnesium oxide.

4 0

3 years ago

9. The formular for finding the area

sukhopar [10]

Answer:

D. length × width

Explanation:

eg. 30 cm(length) × 20cm(width) = 600cm²

4 0

3 years ago

Fill in the coefficients that will balance the following reaction a0h2so4 + a1koh → a2k2so4 + a3hoh

Anuta_ua [19.1K]

A0 = 1
a1 = 2
a2 = 1
a3 = 2

This can be solved by guessing and checking and making sure that all atoms on the left side are accounted for on the right side. Both sides must have the same amount of atoms or the balancing is not correct.

7 0

3 years ago

Read 2 more answers