Answer:
0.2544 moles of water were removed from the sample by the heating process.
Explanation:
Mass of empty evaporating dish = 9.687 g
Mass of evaporating dish and sample of hydrate = 18.407 g
Mass of hydrate = 18.407 g - 9.687 g = 8.72 g
Mass of the evaporating dish and hydrate after heating = 14.007 g
14.007 g = mass of dish + mass of dehydrate
Mass of dehydrate = 14.007 g - 9.867 g = 4.14 g
Mass of water evaporated = hydrated sample - dehydrated sample
= 8.72 g - 4.14 g = 4.58 g
Moles of water evaporated :
0.2544 moles of water were removed from the sample by the heating process.
Answer:
There are three rules on determining how many significant figures are in a number:
Non-zero digits are always significant.
Any zeros between two significant digits are significant.
A final zero or trailing zeros in the decimal portion ONLY are significant.
The investigation was carried out to explore the effect of amylase on the starch that is present in a substance. The IKI solution reacts with starch to give a dark blue color.
We wait 10 minutes before adding the IKI solution to give the amylase sufficient time to act on the starch present, so that a false negative for the presence of starch is not obtained.
It will deflate because the cold molecules will become closer together
Answer:
The concentration of monosodium phosphate is 0.1262M
Explanation:
The buffer of H₂PO₄⁻ / HPO₄²⁻ (Monobasic phosphate and dibasic phosphate has a pKa of 7.2
To determine the pH you must use Henderson-Hasselbalch equation:
pH = pKa + log [A⁻] / [HA]
<em>Where [A⁻] is molarity of the conjugate base of the weak acid, [HA].</em>
For H₂PO₄⁻ / HPO₄⁻ buffer:
pH = 7.2 + log [HPO₄⁻² ] / [H₂PO₄⁻]
As molarity of the dibasic phosphate is 0.2M and you want a pH of 7.4:
7.4 = 7.2 + log [0.2] / [H₂PO₄⁻]
0.2 = log [0.2] / [H₂PO₄⁻]
1.58489 = [0.2] / [H₂PO₄⁻]
[H₂PO₄⁻] = 0.1262M
<h3>The concentration of monosodium phosphate is 0.1262M</h3>
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