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3 years ago

Thomas has 235 grams of K2S in the chemistry lab. How many atoms of potassium (K) are in 235 grams of the compound?

Chemistry

1 answer:

iVinArrow [24]3 years ago

4 0

The number of atoms of K that are in 235 g of the compound is

2.57 x10^24 atoms

calculation

Step 1: find the moles of K2S

= moles = mass/molar mass

= 235 g/110 g/mol= 2.136 moles

Step 2: multiply 2.136 moles by no. of K atoms in K2S

= 2.136 x2 = 4.272 moles

Step 3: use the Avogadro's law to determine number of K atoms

that is according to Avogadro's law 1 mole = 6.02 x 10^23 atoms

4.272 moles= ? atoms

by cross multiplication

= (4.272 moles x 6.02 x10^23 atoms) / 1 mole = 2.57 x10^24 atoms

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3 years ago

What is the minimum volume of 5.50 M HCl necessary to neutralize completely the hydroxide in 718.0 mL of 0.183 M NaOH

Deffense [45]

The volume of HCl required is 23.89 mL

Calculation of volume:

The reaction:

$HCl + NaOH \rightarrow NaCl + H_2O$

As HCl and NaOH react in 1 : 1 ratio.

Volume of NaOH= 718 mL

Concentration= 0.183M

Volume of HCl= ?

Concentration= 5.50M

Using the dilution formula:

$M_1\times V_1(NaOH)= M_2\times V_2(HCl)$

$0.183\times 718= 5.50 \times V_2\\V_2=\frac{131.394}{5.50} \\V_2 = 23.89 \,mL$

Therefore,

Volume of HCl required will be 23.89 mL.

Learn more about neutralization reaction here,

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6 0

1 year ago

What are essential and non essential proteins ?

katen-ka-za [31]

Nonessential amino acids can be made by the body, while essential amino acids cannot be made by the body so you must get them from your diet.
Nonessential acids : glutamine, proline, glycine etc
Essential acids: lysine, leucine etc.

6 0

3 years ago

0.50 mol A, 0.60 mol B, and 0.90 mol C are reacted according to the following reaction

algol [13]

Reactant C is the limiting reactant in this scenario.

Explanation:

The reactant in the balanced chemical reaction which gives the smaller amount or moles of product is the limiting reagent.

Balanced chemical reaction is:

A + 2B + 3C → 2D + E

number of moles

A = 0.50 mole

B = 0.60 moles

C = 0.90 moles

Taking A as the reactant

1 mole of A reacted to form 2 moles of D

0.50 moles of A will produce $\frac{2}{1}$ = $\frac{x}{0.50}$

thus 0.50 moles of A will produce 1 mole of D

Taking B as the reactant

2 moles of B reacted to form 2 moles of D

0.60 moles of B reacted to form x moles of D

$\frac{2}{2}$ = $\frac{x}{0.6}$

x = 2 moles of D is produced.

Taking C as the reactant:

3 moles of C reacted to form 2 moles of D

O.9 moles of C reacted to form x moles of D

$\frac{2}{3}$ = $\frac{x}{0.9}$

= 0.60 moles of D is formed.

Thus C is the limiting reagent in the given reaction as it produces smallest mass of product.

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3 years ago

Disadvantages of Mendeleev's periodic table

mestny [16]

Answer:

Various limitations of Mendeleev's periodic table are:-

Position of hydrogen - he couldn't assign a correct position to hydrogen as it showed properties of both alkali and halogens .

Position of isotopes - he considered that the properties of elements are a function of their atomic masses. Hence isotopes of a same element couldn't be placed.

In the d-block , elements with lower atomic number were placed before higher atomic number.

Explanation:

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2 years ago