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3 years ago

10

A teacher wants to figure out the amount of a solution that is needed for a titration experiment in a class lab. The class has 1

5 students, and each experiment needs 50 mL of solution.
If each student will perform the experiment two times, how many mL of solution will the teacher need for the whole class?

2 answers:

LUCKY_DIMON [66]3 years ago

7 0

The correct answer is C. 1500 mL on e2020.

zmey [24]3 years ago

6 0

You need to multiply 15 by 2 since each student is doing 2 trials which gives you 30 (you can think of it as 30 students doing it once if that helps you). Then you have to multiply 30 by 50 since the experiment is being done 30 times and each time requires 50mL which equals 1500mL.
Therefore the teacher needs to make 1500mL of solution for the lab.

I hope this helps.

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Explanation:

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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

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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.

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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 :

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(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

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3 years ago

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The enthalpy of the reaction is 64.9 kJ/mol.

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aksik [14]

The question is incomplete, the complete question is;

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Gene, Chromosome, Nucleus

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