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posledela
3 years ago
7

Please help me out!!!

Chemistry
2 answers:
noname [10]3 years ago
6 0
What subject is this ?
marta [7]3 years ago
3 0
Normally these questions ask for the empirical formula of the compound. You want mass%, so you get mass%:
Mass C in 7.93mg CO2
Molar mass CO2 = 12.011+15.999*2 = 44.009g/mol
Molar mass C = 12.011
Mass C = 12.011/44.009*7.93 = 2.1643mg C

Mass H in 4.87mg H2O
Molar mass H2O = 1.008*2+15.999 = 18.015g/mol
Molar mass H2 = 1.008*2 = 2.016
Mass H in 4.87mg H2O = 2.016/18.015*4.87 = 0.545mg H

Mass O = 5.59 -(2.1643 + 0.545) = 2.8807mg

% mass composition:
C = 2.1643/5.59*100 = 38.71%
H = 0.545/5.59*100 = 9.750%
O = 2.880/5.59*100 = 51.52%
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The new acceleration becomes twice the pervious acceleration.

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3 years ago
Which electrolyte is stronger, NaOH or Ca(OH)2? Why?
nataly862011 [7]

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3 years ago
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5 0
3 years ago
Given the following heats of combustion. CH3OH(l) + 3/2 O2(g) CO2(g) + 2 H2O(l) ΔH°rxn = -726.4 kJ C(graphite) + O2(g) CO2(g) ΔH
sergeinik [125]

Answer:

The standard enthalpy of formation of methanol is, -238.7 kJ/mole

Explanation:

The formation reaction of CH_3OH will be,

C(s)+2H_2(g)+\frac{1}{2}O_2\rightarrow CH_3OH(g),\Delta H_{formation}=?

The intermediate balanced chemical reaction will be,

C(graphite)+O_2(g)\rightarrow CO_2(g), \Delta H_1=-393.5kJ/mole..[1]

H_2(g)+\frac{1}{2}O_2(g)\rightarrow H_2O(l), \Delta H_2=-285.8kJ/mole..[2]

CH_3OH(g)+\frac{3}{2}O_2(g)\rightarrow CO_2(g)+2H_2O(l) , \Delta H_3=-726.4kJ/mole..[3]

Now we will reverse the reaction 3, multiply reaction 2 by 2  then adding all the equations, Using Hess's law:

We get :

C(graphite)+O_2(g)\rightarrow CO_2(g) , \Delta H_1=-393.5kJ/mole..[1]

2H_2(g)+2O_2(g)\rightarrow 2H_2O(l) ,\Delta H_2=2\times (-285.8kJ/mole)=-571.6kJ/mol..[2]

CO_2(g)+2H_2O(l)\rightarrow CH_3OH(g)+\frac{3}{2}O_2(g) ,\Delta H_3=726.4kJ/mole [3]

The expression for enthalpy of formation of C_2H_4 will be,

\Delta H_{formation}=\Delta H_1+2\times \Delta H_2+\Delta H_3

\Delta H=(-393.5kJ/mole)+(-571.6kJ/mole)+(726.4kJ/mole)

\Delta H=-238.7kJ/mole

The standard enthalpy of formation of methanol is, -238.7 kJ/mole

4 0
3 years ago
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