Answer:
0.084 M
Explanation:
Using the Henderson-Hasselbalch equation for a buffer ( a buffer is solution contain a weak acid and it conjugate base; the solution resist change in pH)
pH = pKa + log ( base/acid)
4.9 - 4.76 =log ( base / acid)
10^0.14 = ( base / acid)
1.38 = (base / acid)
since there is 0.2 M in the buffer solution
the concentration of acid = 
× 0.2 = 0.084 M
Answer:
Classifying stars according to their spectrum is a very powerful way to begin to understand how they work. As we said last time, the spectral sequence O, B, A, F, G, K, M is a temperature sequence, with the hottest stars being of type O (surface temperatures 30,000-40,000 K), and the coolest stars being of type M (surface temperatures around 3,000 K). Because hot stars are blue, and cool stars are red, the temperature sequence is also a color sequence. It is sometimes helpful, though, to classify objects according to two different properties. Let's say we try to classify stars according to their apparent brightness, also. We could make a plot with color on one axis, and apparent brightness on the other axis, like this:
Explanation:
Disaccharide forms when two monomers join.
At STP volume is 22.4 L
Molar mass NO₂ = 46.0 g/mol
1 mole ---------- 22.4 L
? mole ---------- 11.4 L
moles = 11.4 * 1 / 22.4
moles = 11.4 / 22.4
= 0.5089 moles of NO₂
Mass NO₂ :
moles NO₂ * molar mass
0.5089 * 46.0
= 23.4094 g of NO₂
hope this helps!
