What is the molarity of NaOH if 83.5 mL of NaOH is needed to react with 35.0mL of a 0.275 M solution of H2SO4?
1 answer:
Answer:
0.231 mol/L
Explanation:
The first step is to write the balanced equation for this reaction:
The second step is to find the number of moles in the acid:
number of moles = volume * concentration
= 0.035 L * 0.275 mol/L
= 0.009625 mol
The third step is to use the molar ratio from the balanced chemical equation to find the number of moles of NaOH that can neutralize 0.009625 mol of sulphuric acid.
n(sulphuric acid) : n(sodium hydroxide)
1 : 2
0.009625 mol : x
x = 0.01925 mol
Fourth step is to calculate the concentration of sodium hydroxide:
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Explanation:
- Evaporation is defined as a process in which liquid state of water is changing into vapor state.
So, we need to break the bonds of liquid substance in order to convert it into vapor state. And, energy is absorbed for breaking of bonds which means that evaporation is an endothermic process.
Hence, the statement evaporation of water is an exothermic process is false.
- When a hydrocarbon reacts with oxygen and leads to the formation of carbon dioxide and water then this type of reaction is known as combustion reaction.
A combustion reaction will always release heat energy. Hence, combustion reaction is exothermic in nature.
- When energy is transferred as heat from the surroundings to the system then it means energy is being absorbed by the system. And, absorption of heat is an endothermic process for which
is positive.
- Whereas when energy is transferred from system to the surrounding then it means energy is released by the system which is an exothermic process.
Hence, for an exothermic process value of is negative.
Thus, we can conclude that statements which are true are as follows.
- A combustion reaction is exothermic.
- When energy is transferred as heat from the system to the surroundings,
- For an endothermic reaction Deta H is positive.
Answer:
Explanation:
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In this case, since the equation we use to model the heat exchange into the calorimeter and compute the heat of reaction is:
We plug in the mass of water, temperature change and specific heat to obtain:
Now, this enthalpy of reaction corresponds to the combustion of propyne:
Whose enthalpy change involves the enthalpies of formation of propyne, carbon dioxide and water, considering that of propyne is the target:
However, the enthalpy of reaction should be expressed in kJ per moles of C3H4, so we divide by the appropriate moles in 7.00 g of this compound:
Now, we solve for the enthalpy of formation of C3H4 as shown below:
So we plug in to obtain (enthalpies of formation of CO2 and H2O are found on NIST data base):
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