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3 years ago

Who made polio vaccine

2 answers:

8 0

The polio vaccination was created by a polish-American named Albert Sabin. But the vaccine was discovered by Jonas Salk.

yulyashka [42]3 years ago

5 0

The creator of the Polio Vaccine was Jonas Salk.

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A laboratory technician combined sodium hydroxide with excess iron(II) nitrate. A reaction took place according to this chemical

Whitepunk [10]

The initial mass of sodium hydroxide is 3.3 g (answer C)

calculation

Step 1 : find the moles of iron (ii) hydroxide ( Fe(OH)₂

moles = mass÷ molar mass

from periodic table the molar mass of Fe(OH)₂ = 56 + [16 +1]2 = 90 g/mol

moles is therefore = 3.70 g÷ 90 g/mol = 0.041 moles

Step 2: use the mole ratio to calculate the moles of sodium hydroxide (NaOH)

from given equation NaOH : Fe(OH)₂ is 2 :1

therefore the moles of NaOH = 0.041 x 2 = 0.082 moles

Step 3: find mass of NaOH

mass = moles x molar mass

from the periodic table the molar mass of NaOH = 23 +16 +1 = 40 g/mol

mass = 0.082 moles x 40 g/mol = 3.3 g ( answer C)

8 0

3 years ago

An analytical chemist is titrating of a solution of propionic acid with a solution of 224.9 ml of a 0.6100M solution of propioni

Svetllana [295]

Answer: The pH of acid solution is 4.58

Explanation:

To calculate the number of moles for given molarity, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution (in mL)}}$ .....(1)

For KOH:

Molarity of KOH solution = 1.1000 M

Volume of solution = 41.04 mL

Putting values in equation 1, we get:

$1.1000M=\frac{\text{Moles of KOH}\times 1000}{41.04}\\\\\text{Moles of KOH}=\frac{1.1000\times 41.04}{1000}=0.04514mol$

For propanoic acid:

Molarity of propanoic acid solution = 0.6100 M

Volume of solution = 224.9 mL

Putting values in equation 1, we get:

$0.6100M=\frac{\text{Moles of propanoic acid}\times 1000}{224.9}\\\\\text{Moles of propanoic acid}=\frac{0.6100\times 224.9}{1000}=0.1372mol$

The chemical reaction for propanoic acid and KOH follows the equation:

$C_2H_5COOH+KOH\rightarrow C_2H_5COOK+H_2O$

Initial: 0.1372 0.04514

Final: 0.09206 - 0.04514

Total volume of solution = [224.9 + 41.04] mL = 265.94 mL = 0.26594 L (Conversion factor: 1 L = 1000 mL)

To calculate the pH of acidic buffer, we use the equation given by Henderson Hasselbalch:

$pH=pK_a+\log(\frac{[\text{salt}]}{[acid]})$

$pH=pK_a+\log(\frac{[C_2H_5COOK]}{[C_2H_5COOH]})$

We are given:

$pK_a$ = negative logarithm of acid dissociation constant of propanoic acid = 4.89

$[C_2H_5COOK]=\frac{0.04514}{0.26594}$

$[C_2H_5COOH]=\frac{0.09206}{0.26594}$

pH = ?

Putting values in above equation, we get:

$pH=4.89+\log(\frac{(0.04514/0.26594)}{(0.09206/0.26594)})\\\\pH=4.58$

Hence, the pH of acid solution is 4.58

7 0

3 years ago

What does vinegar do to eggs

andre [41]

Eggshells are made primarily of calcium carbonate. The acid in vinegar softens the calcium of the eggshell. Adding a little vinegar to the water when boiling eggs is an old cook’s trick that makes them easier to peel.

A link to this experiment is below in the comment box

7 0

3 years ago

Molodets [167]

Answer: The temperature does effect the growth of the plants. If you kept them all at different temperature and the growth was different then the temperature is definitly a factor in plant growth

Explanation:

7 0

3 years ago

Several science students were about to conduct an experiment on electricity. The teacher passed on the science activity which cl

olganol [36]

C. You should ALWAYS ask the teacher if you don't get something; your friends could be wrong, don't guess it, and NEVER cheat. Hope this helps!!

8 0

3 years ago