I believe the correct answer true. According to the law of conservation of mass, in a chemical reaction the total starting mass of all the reactants equals the total final mass of all the products. This law states that mass cannot be created or be destroyed. So, the total mass that goes in a process should be equal to the mass that goes out the process. This is true for chemical reactions and physical processes. It is Antoine Lavoisier who described this and is a basic principle used in physics and in chemistry. Mass, unlike energy, cannot be transformed to any form so however the transformation happens the mass should be constant.
In writing the formula for a salt the symbol of the cation is first then the anion is written second .
Find moles of MgSO4.7H2O
molar mass = 246
so moles = 32 / 246 = 0.13 moles.
When heated, all 7 H2O from 1 molecule will be gone.
total moles of H2O present = 7 x 0.13 = 0.91
mass of those H2O = 0.91 x 18 = 16.38g
so mass of anyhydrous MgSO4 remain = 32 - 16.38 = 15.62 g
Answer:
41.3 minutes
Explanation:
Since the reaction is a first order reaction, therefore, half life is independent of the initial concentration, or in this case, pressure.

So, fraction of original pressure = 
n here is number of half life
therefore, 
⇒ n= 3
it took 124 minutes to drop pressure to 1/8 of original value, half life = 124/3= 41.3 minutes.
H2SO4 + 2 NaOH ----> Na2SO4 + 2 H2O.
0.085 L * 0.176 mol/L = 0.01496 mol H2SO4
is neutralised by 0.01496 mol * 2
= 0.02992 mol NaOH.
1000 mL of 0.492 M NaOH
contains 0.492 moles NaPH.
0.02992 / 0.452 * 1000 mL
= 66.19 = 66 mL