Answer:
The correct answer is 25 mL graduated cylinder (it should be used in all the cases)
Explanation:
In order to measure 25.00 ml sample of a solution it should be used a 25 mL graduated cylinder, as it is previously and properly calibrated. The other laboratory glassware, beaker and erlenmeyer, have graduations which are approximate, so they are used when exact volumes are not needed.
ii) graduated cylinder has the least uncertainly. It is more accurate than a beaker or erlenmeyer (to within 1%)
iii) A 25 mL graduated cylinder should be used because it is the most accurate lab glassware (between those were mentioned: beaker, erlenmeyer).
Explanation:
Equation of the reaction:
Br2(l) + Cl2(g) --> 2BrCl(g)
The enthalpy change for this reaction will be equal to twice the standard enthalpy change of formation for bromine monochloride, BrCl.
The standard enthalpy change of formation for a compound,
ΔH°f, is the change in enthalpy when one mole of that compound is formed from its constituent elements in their standard state at a pressure of 1 atm.
This means that the standard enthalpy change of formation will correspond to the change in enthalpy associated with this reaction
1/2Br2(g) + 1/2Cl2(g) → BrCl(g)
Here, ΔH°rxn = ΔH°f
This means that the enthalpy change for this reaction will be twice the value of ΔH°f = 2 moles BrCl
Using Hess' law,
ΔH°f = total energy of reactant - total energy of product
= (1/2 * (+112) + 1/2 * (+121)) - 14.7
= 101.8 kJ/mol
ΔH°rxn = 101.8 kJ/mol.
<span>C4H4
The compound in question has an equal ratio of hydrogen and carbon. The atomic weight of carbon is roughly 12 and the atomic weight of hydrogen is roughly 1. The mass of the compound in question is roughly 52.
52/13=4
C4H4</span>
