The mass ca(Oh)2 needed to produce 1.5 l of 0.25 solution is calculated as follows
find moles
=moles = molarity x volume
moles is therefore = 1.5 x 0.25 = 0.375 moles
mass = moles x molar mass
0.375mol x 74.09 g/mol = 27.78 grams
Answer:
rate = [NO]²[O2]
Explanation:
The rate law for the reaction:
2 NO(g) + O2(g) → 2 NO2(g)
Is expressed in terms of reactants as follows:
rate = [NO]ⁿ[O2]ˣ
<em>Where n and x are the coefficients of the rate law.</em>
<em />
If [NO] is doubled, the rate increased 4 times. That is only possible if:
rate = [NO]²[O2]ˣ
Now, as [NO] is doubled and increased the rate 4 times, and [NO] + [O2] when doubled increased the rate 8 times, doubled [O2] implies increased the rate 2 times. That is only possible is:
<h3>rate = [NO]²[O2]</h3>
Since the sample size is below 30, in this case we use
the t statistic. The formula for t score is:
t = (x – u) / (σ / sqrt n)
where,
x = the level l = unknown
u = sample mean = 120 mg / dl
σ = standard deviation = 20 mg / dl
n = sample size or number of results = 5
Using the standard distribution tables for t, we can find
the value of t given the probability (P = 0.15) and degrees of freedom (DOF).
t = 1.036
Going back to the
formula for t score:
1.036 = (x – 120)
/ (20 / sqrt 5)
x = 129.27 mg /
dl = l
Oxygen is the most abundant by weight
Yes, it is. The pencil is still composed of wood and graphite before and after the break, although the physical form is different, of course. If you wanted a comparison, burning the pencil would be a chemical change.