The answer is d but can anyone explain why and if not don't answer

What is the pH when 10.0 mL of 0.20 M potassium hydroxide is added to 30.0 mL of 0.10 M cinnamic acid, HC9H7O2 (Ka = 3.6 × 10–5)

astra-53 [7]

Answer:-

Solution:- As is clear from the given Ka value, Cinnamic acid is a weak acid. let's calculate the moles of acid and KOH added to it from their given molarities and mL.

For KOH, $10.0mL(\frac{1L}{1000mL})(\frac{0.20mol}{1L})$

= 0.002 mol

For Cinnamic acid, $30.0mL(\frac{1L}{1000mL})(\frac{0.10mol}{1L})$

= 0.003 mol

Acid and base react as:

$HC_9H_7O_2(aq)+KOH(aq)\rightleftharpoons KC_9H_7O_2(aq)+H_2O(l)$

The reaction takes place in 1:1 mol ratio. Since the moles of acid are in excess, the acid is still remaining when all the kOH is used.

0.002 moles of KOH react with 0.002 moles of Cinnamic acid to form 0.002 moles of potassium cinnamate. Excess moles of Cinnamic acid = 0.003 - 0.002 = 0.001

As the solution have weak acid and it's salt(or we could say conjugate base), it is a buffer solution and the pH of the buffer solution could easily be calculated using Handerson equation:

$pH=pKa+log(\frac{base}{acid})$

pKa could be caluted from given Ka value using the formula:

pKa = - log Ka

$pKa=-log3.6*10^-^5$

pKa = 4.44

let's plug in the values in Handerson equation and calculate the pH:

$pH=4.44+log(\frac{0.002}{0.001})$

pH = 4.44+0.30

pH = 4.74

So, the first choice is correct, pH is 4.74.

6 0

3 years ago

Which of these is a mixture?? A.) salad B.) potassium C.) water D.) sugar

tensa zangetsu [6.8K]

Salad would be a mixture because it is not chemically combined, if needed you could physically take it apart. So your answer would be A.)

8 0

4 years ago

Read 2 more answers

Select the correct answer. Which substance is made of polymers? A. marble B. protein C. salt D. steel

Greeley [361]

Answer:

the answer is B proteins

Explanation:

brainliest pls

4 0

3 years ago

Read 2 more answers

How does Silicon shape our technological reality

Vladimir79 [104]

Silicons are used in our day to day technology products.It is used used to micro-chips and motherboards and other components on nano-technologies.

3 0

3 years ago

What is the percent yield for a process in which 10.4g of CH3OH reacts and 10.1 g of CO2 is formed

monitta

Answer:

A. 70.7%

Explanation:

In the first step lets compute the molar mass of CH₃OH and CO

Molar Mass of CH₃OH = 1(12.01 g/mol) + 4(1.008 g/mol) +1(16.00 g/mol)

= 32.042 g/mol

Molar Mass of CO₂ = 1(12.01 g/mol) + 2(16.00 g/mol)

= 44.01 g/mol

Mass of only one reactant i.e. CH₃OH is given so it must be the limiting reactant. Next, the theoretical yield is calculated directly as follows:

Given mass of CH₃OH is 10.4 g. So we have:

10.4g CH₃OH

Convert grams of CH₃OH to moles of CH₃OH utilizing molar mass of CH₃OH as:

1 mol CH₃OH / 32.042 g CH₃OH

Convert CH₃OH to moles of CO₂ using mole ratio as:

2 mol CO₂ / 2 mol CH₃OH

Convert moles of CO₂ to grams of CO₂ utilizing molar mass of CO₂ as:

44.01 g/mol CO₂ / 1 mol CO₂

Now calculating theoretical yield using above steps:

[ 10.4 g CH₃OH ] [1 mol CH₃OH / 32.042 g CH₃OH ] [2 mol CO₂ / 2 mol CH₃OH] [44.01 g/mol CO₂ / 1 mol CO₂]

Multiplication is performed here. We are left with 10.4 and 44.01 g CO₂ from numerator terms in the above equation and 32.042 from denominator terms after cancellation process of above terms. So this equation becomes:

= ( 10.4 ) ( 44.01 ) g CO₂ / 32.042

= 457.704/32/042

= 14.28 g CO₂

Theoretical yield = 14.28 g CO₂

Finally compute the percent yield for a process in which 10.4g of CH₃OH reacts and 10.1 g of CO₂ is formed:

percent yield = (actual yield / theoretical yield) x 100

As we have calculated theoretical yield which is 14.28 g CO₂ and actual yield is 10.1 g CO₂ So,

percent yield = (10.1 g CO₂ / 14.28 g CO₂) x 100%

= 0.707 x 100%

= 70.7 %

Hence option A 70.7% yield is the correct answer.

8 0

4 years ago