Half-life time of a reaction is time at which reactant concentration becomes half of its initial value.
Half-life of the first order reaction is 20 min. Rate constant can be calculated as follows:
![K=\frac{0.6932}{t_{1/2}}=\frac{0.6932}{20 min}=0.03466 min^{-1}](https://tex.z-dn.net/?f=K%3D%5Cfrac%7B0.6932%7D%7Bt_%7B1%2F2%7D%7D%3D%5Cfrac%7B0.6932%7D%7B20%20min%7D%3D0.03466%20min%5E%7B-1%7D)
The rate expression for first order reaction is as follows:
![k=\frac{2.303}{t}log\frac{A_{0}}{A_{t}}](https://tex.z-dn.net/?f=k%3D%5Cfrac%7B2.303%7D%7Bt%7Dlog%5Cfrac%7BA_%7B0%7D%7D%7BA_%7Bt%7D%7D)
initial number of molecules of reactant are
, time is 100 min thus, putting the values to calculate number of reactant at time 100 min,
![0.03466 min^{-1}=\frac{2.303}{100 min}log\frac{[10^{20}]}{A_{t}}](https://tex.z-dn.net/?f=0.03466%20min%5E%7B-1%7D%3D%5Cfrac%7B2.303%7D%7B100%20min%7Dlog%5Cfrac%7B%5B10%5E%7B20%7D%5D%7D%7BA_%7Bt%7D%7D)
On rearranging,
![\frac{10^{20}}{A_{t}}=31.988](https://tex.z-dn.net/?f=%5Cfrac%7B10%5E%7B20%7D%7D%7BA_%7Bt%7D%7D%3D31.988)
Or,
![A_{t}=3.13\times 10^{18}](https://tex.z-dn.net/?f=A_%7Bt%7D%3D3.13%5Ctimes%2010%5E%7B18%7D)
Therefore, number of molecules unreacted will be ![3.13\times 10^{18}](https://tex.z-dn.net/?f=3.13%5Ctimes%2010%5E%7B18%7D)
Answer:
21.1111 is the right answer
Explanation:
Answer:
The molecules of the liquid collide with the molecules of solid, gradually breaking the bonds between the molecules in the solid and causing the ice to melt.
Answer:
0.250 mol Mg²⁺
0.500 mol Cl⁻
Explanation:
Magnesium chloride (MgCl₂) dissociates into ions according to the following equilibrium:
MgCl₂ ⇒ Mg²⁺ + 2 Cl⁻
1 mol 1 mol 2 mol
1 mol of Mg²⁺ and 2 moles of Cl⁻ are formed per mole of MgCl₂. If we have 0.250 mol of MgCl₂, the following amounts of ions will be formed:
0.250 mol MgCl₂ x 1 mol Mg²⁺/mol MgCl₂= 0.250 mol Mg²⁺
0.250 mol MgCl₂ x 2 mol Cl⁻/mol MgCl₂= 0.500 mol Cl⁻
<h2>d=density, m=mass, v=volume</h2>
1. 17.2kg=17200g
so knowing that d=m/V, use V=m/d to calculate the volume
v=17200/5.75
and then devide by 1000 to convert cm3 to dm3 and the answer will be in dm3
2. d=m/v
v=0.5l
m=425g
so use the formula and you will get d=425/0.5=850g/l
3. use d=m/v again, but not before rewriting the formula for volume: m=vd and convert dm3 to cm3
1dm3=1000cm3
so 0.987dm3 =987 cm3
now m=987cm3 * 10.5g/cm3 and the answer will be in grams