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2 years ago

Which is not true regarding reaction rates? (2 points)

Chemistry

1 answer:

PtichkaEL [24]2 years ago

5 0

Let us consider each statement one by one

a) Catalysts are the substance which alter the reaction pathway where activation energy of reaction is less that the un catalyzed reaction. They are not used up in the reaction . the catalyst is restored in the reaction.

b) As mentioned above, the catalyst speed up reaction by lowering the activation energy

c) During a reaction the reactants are consumed up and products are formed. so there is a decrease in concentration of reactant.

Thus all the above statements are true.

D) the rate of decrease in concentration of reactants depends upon the coefficient of reactant in balanced chemical reaction.

For example

$H_{2} (g) + \frac{1}{2} O_{2} (g) --> H_{2}O(g)$

Here the rate of decrease in concentration of hydrogen will be double the rate of decrease in concentration of oxygen.

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Consider the following reaction.

Ivan

Answer:

162 g Fe₂O₃

Explanation:

To find the mass of Fe₂O₃, you need to (1) convert grams C to moles C (via molar mass from periodic table), then (2) convert moles C to moles Fe₂O₃ (via mole-to-mole ratio from reaction coefficients), and then (3) convert moles Fe₂O₃ to grams (via molar mass). It is important to arrange the ratios/conversions in a way that allows for the cancellation of units. The final answer should have 3 sig figs to reflect the given value.

Molar Mass (C): 12.011 g/mol

2 Fe₂O₃(s) + 3 C(s) ---> 4 Fe(s) + 3 CO₂(g)

Molar Mass (Fe₂O₃): 2(55.845 g/mol) + 3(15.998 g/mol)

Molar Mass (Fe₂O₃): 159.684 g/mol

18.3 g C 1 mole 2 moles Fe₂O₃ 159.684 g
-------------- x ---------------- x ------------------------- x ----------------- = 162 g Fe₂O₃
12.011 g 3 moles C 1 mole

5 0

1 year ago

Is phosphorous dissolving in carbon disulfide a physical or chemical property? if physical, is it intensive or extensive?

Nana76 [90]

Answer: Phosphorus is insoluble in water, but soluble in carbon disulfide. Phosphorus burns spontaneously in air to its pentoxide.

Explanation: Hope this helped! :)

3 0

3 years ago

Read 2 more answers

A student is trying to develop a model of an instant heat pack. What is the essential characteristic of the chemical reaction th

Lana71 [14]

The standard enthalpy of reaction should be negative.

<h3>What is enthalpy?</h3>

A thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume.

Inside the heat pack are two chemicals that get mixed when you smush them together. As they mix, some weak bonds are broken, which takes a little bit of energy. But new, stronger bonds form which release energy. Releasing that energy causes the surroundings to heat up.

Hence, option B is correct.

Learn more about enthalpy here:

brainly.com/question/13775366

#SPJ1

3 0

2 years ago

5.4 When looking down the C{{TOP-HAT-MATH-TOKEN-0}}-C{{TOP-HAT-MATH-TOKEN-1}} bond in 2,3-dimethylbutane, what is the most stabl

AURORKA [14]

Answer:

The most stable conformer would be the anti-conformer when the substituent methyl groups are farthest away from each other.

Explanation:

Isomers are chemical compounds with the same molecular formula but with different molecular structures.

Conformers are a special type of isomers that produce different structures when the substituents of a Carbon-Carbon single bond (C-C) are rotated.

In 2,3 dimethyl butane, the substituent methyl groups are located around the second and third Carbon to Carbon single bond.

To achieve a stable configuration, the methyl group substituents need to be as far apart as possible (that is, in an anti-position) to minimise repulsion.

The closer the methyl groups are to each other, the more they repel each other and the more unstable the conformer becomes.

7 0

2 years ago

How many grams of sodium phosphate monobasic would we add to a liter and how many grams of sodium phosphate dibasic would we add

Nostrana [21]

Answer :

The correct answer for Mass of Na₂HPO₄ = 4.457 g and mass of NaH₂PO₄ = 8.23 g

Given : pH = 6.86

Total concentration of Phosphate buffer = 0.1 M

Asked : Mass of Sodium phosphate monobasic (NaH₂PO₄) = ?

Mass of Sodium phosphate dibasic(Na₂HPO₄)= ?

Following steps can be done to find the masses of NaH₂PO₄ and Na₂HPO₄ :

(In phosphate buffer , Na+ ion from NaH₂PO₄ and Na₂HPO₄ acts as spectator ion , so only H₂PO₄⁻ and HPO₄²⁻ will be considered )

H₂PO₄⁻ <=> HPO₄²⁻

The above reaction has pka = 7.2 ( from image shown )

<u>Step 2 : Plug values in Hasselbalch- Henderson equation </u>.

Hasselbalch -Henderson equation is to find pH for buffer solution which is as follows :

$pH = pka + log\frac{[A^-]}{[HA]}$

pH = 6.86 pKa = 7.2

$6.86 = 7.2 + log \frac{[HPO_4^2^-]}{[H_2PO_4^-]}$

Subtracting both side by 7.2

$6.86-7.2 = 7.2 -7.2+ log \frac{[HPO_4^2^-]}{[H_2PO_4^-]}$

$-0.34 = log \frac{[HPO_4^2^-]}{[H_2PO_4^-]}$

Removing log

$10^-^0^.^3^4 = \frac{[HPO_4^2^-]}{[H_2PO_4^-]}$

$\frac{[HPO_4^2^-]}{[ H_2PO_4^-]} = 0.457$ ---------------- equation (1)

<u>Step 3 : To find molarity of H₂PO₄⁻ and HPO₄²⁻</u>

Total concentration of buffer = [H₂PO₄⁻] + [HPO₄²⁻] = 0.1 M

Hence, [H₂PO₄⁻ ] + [ HPO₄²⁻ ] = 0.1 M

Assume [H₂PO₄⁻ ] = x

So , [x ] + [ HPO₄²⁻ ] = 0.1 M

[ HPO₄²⁻ ] = 0.1 - x

Step 4 : Plugging value of [H₂PO₄⁻ ] and [ HPO₄²⁻ ]

[H₂PO₄⁻ ] = x

[ HPO₄²⁻ ] = 0.1 - x

Equation (1) = > $\frac{[HPO_4^2^-]}{[ H_2PO_4^-]} = 0.457$

Plug value of [H₂PO₄⁻ ] and [ HPO₄²⁻ ] ( from step 3 ) into equation (1) as :

$\frac{[0.1 - x ]}{[ x]} = 0.457$

Cross multiplying

$0.1 - x = 0.457 x$

Adding x on both side

$0.1 -x + x = 0.457 x + x$

$0.1 = 1.457 x$

Dividing both side by 1.457

$\frac{0.1}{1.457} = \frac{1.457 x }{1.457}$

x = 0.0686 M

Hence , [H₂PO₄⁻ ] = x = 0.0686 M

[ HPO₄²⁻ ] = 0.1 - x

[ HPO₄²⁻ ] = 0.1 - 0.0686

[ HPO₄²⁻ ] = 0.0314 M

Step 5 : To find moles of H₂PO₄⁻ ( NaH₂PO₄) and HPO₄²⁻ (Na₂HPO₄ ) .

Molarity is defined as mole of solute per 1 L volume of solution .

Molarity of NaH₂PO₄ = 0.0686 M or 0.0686 mole per 1 L

Molarity of Na₂HPO₄ = 0.0314 M or 0.0314 mole per 1 L

Since that volume of buffer solution is 1 L , so Molarity = mole

Hence Mole of NaH₂PO₄ = 0.0686 mol

Mole of Na₂HPO₄ = 0.0314 mol

Moles of Na₂HPO₄ and NaH₂PO₄ can be converted to their masses using molar mass as follows :

Molar mass of Na₂HPO₄ = $141.96 \frac{g}{mol}$

Molar mass of NaH₂PO₄ = $119.98 \frac{g}{mol}$

$Mass (g) = mole (mol)* molar mass(\frac{g}{mol})$

$Mass of Na_2HPO_4 = 0.0314 mol * 141.96 \frac{g}{mol}$

Mass of Na₂HPO₄ = 4.457 g

$Mass of NaH_2PO_4 = 0.0686 mol * 119.98 \frac{g}{mol}$

Mass of NaH₂PO₄ = 8.23 g

5 0

2 years ago