The initial mass of sodium hydroxide is 3.3 g (answer C)
<u><em>calculation</em></u>
Step 1 : find the moles of iron (ii) hydroxide ( Fe(OH)₂
moles = mass÷ molar mass
from periodic table the molar mass of Fe(OH)₂ = 56 + [16 +1]2 = 90 g/mol
moles is therefore = 3.70 g÷ 90 g/mol = 0.041 moles
Step 2: use the mole ratio to calculate the moles of sodium hydroxide (NaOH)
from given equation NaOH : Fe(OH)₂ is 2 :1
therefore the moles of NaOH = 0.041 x 2 = 0.082 moles
Step 3: find mass of NaOH
mass = moles x molar mass
from the periodic table the molar mass of NaOH = 23 +16 +1 = 40 g/mol
mass = 0.082 moles x 40 g/mol = 3.3 g ( answer C)
The conversions that will be used are:
1 mole of copper / 63.5 grams of copper
6.02 x 10²³ atoms of copper / 1 mole of copper
Multiplying the given mass by these conversions,
660 g * (1 mol Cu / 63.5 g Cu) * (6.02 x 10²³ Cu atoms / 1 mole Cu)
The sample contains 6.25 x 10²⁴ atoms of copper
It should be <em>Ultraviolet rays </em>because they are moderate in energy.
Answer: none
Explanation: there is no picture attached
