What do you mean by chemical reaction ?

Chemistry

1 answer:

kherson [118]3 years ago

6 0

A chemical reaction is a reaction that changes the molecular structure and is normally irreversible.

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A student prepares a lactic acid-sodium lactate buffer solution by mixing 40.mL of 0.50MHC3H5O3(aq) with 200.mL of 1.0M NaC3H5O3

notsponge [240]

Answer:

pH=3.38

Explanation:

We are given the concentrations of the weak acid and its conjugate base so we need to use the henderson hasslebalch equation

pH=pKa + log (concentration A-/concentration of HA)

A- : conjugate base NaC3H5O3

HA: weak acid HC3H5O3

so if we plug in what we are given

pH= 3.08 + log (1M/.5M)

pH= 3.38

8 0

3 years ago

Determine the mass of 5.2 x 10 power of 21 molecules of propanol C3H7OH(l), on grams.

Alja [10]

$n(\text{C}_3\text{H}_7\text{OH}) = N(\text{C}_3\text{H}_7\text{OH}) / N_A\\ \phantom{n(\text{C}_3\text{H}_7\text{OH})} = 5.2 \times 10^{21} / (6.02 \times 10^{23})\\ \phantom{n(\text{C}_3\text{H}_7\text{OH})} = 8.6 \times 10^{-3} \; \text{mol}$

where $N_A = 6.02 \times 10^{23}\; \text{mol}^{-1}$ the Avogadro's constant that relates the number of particles to their number, in the unit moles $\text{mol}$ .

The molar mass of propanol- mass per mole propanol- can be directly deduced from its molecular formula with reference to a modern periodic table.

$M(\text{C}_3\text{H}_7\text{OH}) = \underbrace{3 \times 12.01}_{\text{carbon}} + \underbrace{8 \times 1.008}_{\text{hydrogen}} + \underbrace{1\times 16.00}_{\text{oxygen}} = 60.09 \; \text{g} \cdot \text{mol}^{-1}$

$8.6 \times 10^{-3} \; \text{mol}$ of propanol molecules would thus have a mass of $8.6 \times 10^{-3} \; \text{mol} \times 60.09 \; \text{g} \cdot \text{mol}^{-1} = 0.52 \; \text{g}$