Answer:
147 g
Explanation:
<em>The number of moles of a substance is the ratio of the mass of the substance and the molar mass of that substance.</em> Mathematically,
mole = mass of substance/molar mass
In this case, Nick needs 3.5 moles of NaF, the molar mass of NaF is calculated as:
23 + 19 = 42 g/mol (Note: Na = 23, F = 19)
Hence,
mass of 3.5 mole NaF = mole x molar mass
= 3.5 x 42 = 147 g.
<em>Hence, Nick would need to measure out </em><em>147 g</em><em> NaF using a suitable weighing balance.</em>
B ............ is the answer,
The oxidation number of H is -1.
Sum of the oxidation numbers in each element =
charge of the complex
CaH₂ has 1 Ca atom and 2H atoms. The charge of
the complex is zero. Let’s say Oxidation number of H is "a".
Then,
<span> (+2)
+ 2 x a = 0 </span>
<span> +2 + 2a = 0</span>
2a = -2
a = -1
Hence, the oxidation number of Hydrogen atom in CaH₂ is -1
H2O is the correct answer :)