Answer : Volume of HCl ( in ml) is 10 ml.
Solution : Given, Concentration of NaOH = 0.1 mol/L
Volume of NaOH = 20 ml
Concentration of HCl = 0.2 mol/L
Volume of HCl = ?
Formula used : Moles = Volume × Concentration
In the reaction, we see that 1 mole of NaOH react with the 1 mole of HCl.
so,
Moles of NaOH = Moles of HCl
Moles of HCl = Moles of NaOH = Volume of NaOH ( in L) × Concentration of NaOH
Converstion ml into L : 1000 ml = 1 L
Moles of HCl =
× 0.1
= 0.002 mol
Volume of HCl = Moles / Comcentration of HCl
= 
= 0.01 L
Volume of HCl (in ml) = 0.01 × 1000 = 10 ml
Exchange rate is 2 guilders for every 3 florins
The conversion factor will be
2 guilders / 3 florins = 3 florins / 2 guilders = 1
so if we wish to convert 17 guilders to florins we will use following conversion factor
3 florins / 2 guilders = B / C
D = 17guilders X 3 florins / 2 guilders = 25.5 florins
Answer : The amount of heat needed is, 1188 J
Explanation :
Formula used :

where,
q = heat needed = ?
m = mass of copper = 55 g
c = specific heat capacity of copper = 
= initial temperature = 
= final temperature = 
Now put all the given values in the above formula, we get:


Thus, the amount of heat needed is, 1188 J
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Answer:
The advantages of using an indicator to inform pH measurements:
It gives a mathematically result of the pH, in addition, it gives the precise pH of solvent, and it also gives an idea of the straight of the solution also.
Now, the advantage of using a pH meter:
It is a rapid method to characterize between acids, bases. However, this method does not show how strong acid or base actually are, plus it tends to gives a range of acidity or basicity not quite accurate as a result.