Answer : The formula of the gas produced is,
(phosphine gas)
Explanation :
According to the question, when sodium phosphide is treated with water then it react to give phosphine gas and sodium hydroxide.
The balanced chemical reaction will be:

By Stoichiometry of the reaction we can say that:
1 mole of sodium phosphide reacts with 3 moles of water to give 1 mole of phosphine gas and 3 moles of sodium hydroxide.
Thus, the formula of the gas produced is,
(phosphine gas)
Silicon must have 4 single covalent bond, every single bond has 2 electrons (one pair), so 4·2=8 electrons (octet).
True. A mole of anything has the same amount of molecules. 1 mole = 6.022 x 1023 molecules
Hey there!:
absorbance = log 100 - log Transmitance
absorbace = 0.85
log 100 = 2
- log transmitance = absorbace / log 100
0.85 / 2= 0.425
transmitance = 10 ^ ( - 0.425 )
transmitance = 0.376