It is a physical change because you can not put it back like it was
Answer:
A. 2Na + 2H₂O → 2NaOH + H₂
Explanation:
When sodium is reacted with water, a single replacement reaction occurs. The product of the reaction is typically sodium hydroxide and hydrogen gas.
Reactants:
Sodium + water
Product:
Sodium hydroxide + hydrogen gas
So;
2Na + 2H₂O → 2NaOH + H₂
Answer:
The answer is SiO2
Explanation:
Silocon dioxide is written without a 1 after the silocon and with a 2 after the oxygen.
Answer: The mass percentage of 
is 5.86%
Explanation:
To calculate the mass percentage of in the sample it is necessary to know the mass of the solute ( in this case), and the mass of the solution (pesticide sample, whose mass is explicit in the letter of the problem).
To calculate the mass of the solute, we must take the mass of the 
precipitate. We can establish a relation between the mass of and using the stoichiometry of the compounds:
Since for every mole of Tl in there are two moles of Tl in , we have:
Using the molar mass of we have:
Finally, we can use the mass percentage formula:
The liters in 3.25 g of ammonia 4.28 L
<u><em>calculation</em></u>
Step 1: find moles of ammonia
moles = mass÷ molar mass
From periodic table the molar mass of ammonia (NH₃) = 14 +(1×3 ) = 17 g/mol
3.25 g÷ 17 g/mol = 0.191 moles
Step 2: find the number of liters of ammonia
that is at STP 1 moles = 22.4 L
0.191 moles = ? L
<em>by cross multiplication</em>
={( 0.191 moles ×22.4 L) / 1 mole} = 4.28 L
