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4 years ago

8

True or false? A chemical change involves an energy change.

2 answers:

hoa [83]4 years ago

8 0

Whether a chemical reaction absorbs or releases energy, there is no overall change in the amount of energy during the reaction. I believe that your answer is to be true.

skad [1K]4 years ago

4 0

The answer is true a chemical change does not involve a energy change.

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Determine the enthalpy change for the decomposition of calcium carbonate. CaCO₃(s) --> CaO(s) + CO₂(g) given the thermochemic

Hunter-Best [27]

Answer: c. 179 kJ/mol

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 Hess’s law, the chemical equation can be treated as algebraic expressions 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.

Given:

$Ca(OH)_2(s)\rightarrow CaO(s)+H_2O (l)$ $\Delta H_1= 65.2 kJ/mol$ (1)

$Ca(OH)_2(s)+CO_2(g)\rightarrow CaCO_3(s)+H_2O(l)$ $\Delta H_2= -113.8 kJ/mol$ (2)

$C(s)+O_2(g)\rightarrow CO_2(g)$ $\Delta H_3= -393.5 kJ/mol$ (3)

$2Ca(s)+O_2(g)\rightarrow 2CaO(s)$ $\Delta H_4=-1270.2 kJ/mol$ (4)

On subtracting eq (1) from eq (2) we have:

$Ca(OH)_2(s)\rightarrow CaO(s)+H_2O(l)$ - $Ca(OH)_2(s)+CO_2(g)\rightarrow CaCO_3(s)+H_2O(l)$

$CaCO_3(s)\rightarrow CaO(s)+CO_2(g)$

$\Delta H=-113.8-(65.2)kJ/mol=-179kJ/mol$

Hence the enthalpy change for the raection is 179.0 kJ/mol.

6 0

3 years ago

The kilocalories in one can of cola if it has 40. g of carbohydrate and no fat or<br> protein

Marysya12 [62]

Answer:

One can of cola contain 0.16 kcal of carbohydrates.

Explanation:

Given data:

mass of cola can = 40 g

kilocalories of carbohydrates = ?

Solution:

we know that there are 4 cal of carbohydrates per gram.

40 g × 4 cal/g = 160 cal

Now we will convert calories into kilocalories. There are 1000 calories in one kilocalories so,

160/1000 = 0.16 kcal

so, one can of cola contain 0.16 kcal of carbohydrates.

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3 years ago

An alien civilization has different names and symbols for six elements. Place each element in the correct location in the period

Margarita [4]

Answer:

why whould I know that!!??

Explanation:

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3 years ago

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Leopards and cheetahs look very similar, since both have spotted coats, but the two species of big cats are actually quite diffe

Lisa [10]

The answer is letter A i think

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3 years ago

Look at these two molecular diagrams and think about the features of the compounds.

Masteriza [31]

Answer:

a. are isomers of each other

b. have same molecular formula

d. are both hydrocarbons

e. have same number of each kind of atom

Explanation:

hope this helps!

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3 years ago

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