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Which statments are true about balancing chemical reactions?

frez [133]

D atoms that are in only one of the reactions and only one of the products should be down first

3 0

2 years ago

As the temperature of a gas increases, explain what happens to its density and why.

Ghella [55]

Answer:

When a gas is heated, the molecules move faster, bump into each other, and spread apart. Because the molecules are spread apart, they take up more space. They are less dense.

3 0

2 years ago

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Find the standard enthalpy of formation of ethylene, C2H4(g), given the following data: C2H4(g) + 3 O2(g) --> 2CO2(g) + 2 H2O

Brums [2.3K]

Answer : The standard enthalpy of formation of ethylene is, 52.4 kJ

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.

The formation reaction of $C_2H_4$ will be,

$2C(s)+2H_2(g)\rightarrow C_2H_4(g)$ $\Delta H_{formation}=?$

The intermediate balanced chemical reaction will be,

(1) $C_2H_4(g)+3O_2(g)\rightarrow 2CO_2(g)+2H_2O(l)$ $\Delta H_1=-1411kJ$

(2) $C(s)+O_2(g)\rightarrow CO_2(g)$ $\Delta H_2=-393.5kJ$

(3) $H_2(g)+\frac{1}{2}O_2(g)\rightarrow H_2O(l)$ $\Delta H_3=-285.8kJ$

Now we will reverse the reaction 1, multiply reaction 2 and 3 by 2 then adding all the equation, we get :

(1) $2CO_2(g)+2H_2O(l)\rightarrow C_2H_4(g)+3O_2(g)$ $\Delta H_1=+1411kJ$

(2) $2C(s)+2O_2(g)\rightarrow 2CO_2(g)$ $\Delta H_2=2\times (-393.5kJ)=-787kJ$

(3) $2H_2(g)+2O_2(g)\rightarrow 2H_2O(l)$ $\Delta H_3=2\times (-285.8kJ)=-571.6kJ$

The expression for enthalpy of formation of $C_2H_4$ will be,

$\Delta H_{formation}=\Delta H_1+\Delta H_2+\Delta H_3$

$\Delta H=(+1411kJ)+(-787kJ)+(-571.6kJ)$

$\Delta H=52.4kJ$

Therefore, the standard enthalpy of formation of ethylene is, 52.4 kJ

7 0

3 years ago

Description of how the combined gas law must be modified to introduce the number of moles

telo118 [61]

So the ideal gas law is pv=nrt
The letter n stands for the number of moles. divide both side by rt to isolate.
pv/rt=n

8 0

3 years ago

Marvin records scientific data about Lake Superior. For which property has Marvin forgotten to use an SI unit of measurement?

Illusion [34]

Answer: low temperature

Explanation:-

S.I or M.K.S is a system for defining physical units as meter, kilogram, second, ampere, kelvin or celcius, candela, and mole together with a set of prefixes to indicate multiplication or division by a power of ten for measuring length, mass, time , current, temperature and amount of substance respectively.

Given :

lake length = 563 kilometers = $563\times 10^3m$

High temperature = $76.5^0F$

Low temperature = $-6.3^0C$

annual precipitation =762 mm= $762\times 10^{-3}m$

Thus low temperature in units of Fahrenheit is not an S.I unit of measurement.

8 0

3 years ago

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