2AgNO3 + Ni2+ = Ni(NO3)2 + 2Ag<span>+</span>
From the reaction,
it can be seen that AgNO3 and Ni2+ has following amount of substance
relationshep:
n(AgNO3):n(Ni)=2:1
From the relationshep we can determinate requred moles of Ni2+:
n(AgNO3)=m/M= 15.5/169.87=0.09 moles
So, n (Ni)=n(AgNO3)/2=0.045 moles
Finaly needed mass of Ni2+ is:
m(Ni2+)=nxM=0,045x58.7=2.64g
The answer is A. because as you can see it pulls the force
Answer:
The SI base unit for amount of substance is the mole. 1 grams NaOH is equal to 0.025001806380511 mole.
Standard temperature is 273 K
Standard pressure is 1 atm
We use the ideal gas equation to find out density of nitrogen gas in g/L
Ideal gas equation:

Molar mass of 
Pressure = 1 atm
Temperature = 273 K

= 1.25 g/L
Therefore, density of nitrogen gas at STP is 1.25 g/L