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3 years ago

This is the last week of school for me and i need help pleaseee !!

Chemistry

1 answer:

viktelen [127]3 years ago

6 0

Answer:

The reaction in the cold pack is an endothermic reaction

Explanation:

An endothermic reaction is a reaction that absorbs energy (heat) from the surrounding to supply the required energy of activation that allows the occurrence of the reaction

Therefore, when a reaction is endothermic, it boundary or the system where the reaction is occurring feels cold to touch

Hence, the reaction in the cold pack is an endothermic reaction.

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How many molecules are present in a drop of ethanol, c2h5oh, of mass 2.3*10^-2.3g? (NA=6.0*10^23mol^-1)

sdas [7]

Answer:

3.0 × 10²⁰ molecules

Explanation:

Given data:

Mass of ethanol = 2.3 × 10⁻²°³ g

Number of molecules = ?

Solution:

Number of moles of ethanol:

Number of moles = mass/ molar mass

Number of moles = 2.3 × 10⁻²°³ g / 46.07 g/mol

Number of moles = 0.05 × 10⁻²°³ mol

Number of molecules:

One mole = 6.022 × 10²³ molecules

0.05 × 10⁻²°³ mol × 6.022 × 10²³ molecules / 1 mol

0.30 × 10²⁰°⁷ molecules

3.0 × 10¹⁹°⁷ molecules which is almost equal to 3.0 × 10²⁰ molecules.

5 0

3 years ago

A solution of HNO3HNO3 is standardized by reaction with pure sodium carbonate. 2H++Na2CO3⟶2Na++H2O+CO2 2H++Na2CO3⟶2Na++H2O+CO2 A

Gemiola [76]

Answer:

(0,653±0,002) M of HNO₃

Explanation:

The reaction of standarization of HNO₃ with Na₂CO₃ is:

2 HNO₃ + Na₂CO₃ ⇒ 2 Na⁺ + H₂O + CO₂ + 2NO₃⁻

To obtain molarity of HNO₃ we need to know both moles and volume of this acid. The volume is (27,71±0,05) mL and to calculate the moles it is necessary to obtain the Na₂CO₃ moles and then convert these to HNO₃ moles, thus:

0,9585 g of Na₂CO₃ × ( 1 mole / 105,988 g) =

9,043×10⁻³ mol Na₂CO₃ × ( 2 moles of HNO₃ / 1 mole of Na₂CO₃) = 1,809×10⁻² moles of HNO₃

Molarity is moles divide liters, thus, molarity of HNO₃ is:

1,809×10⁻² moles / 0,02771 L = 0,6527 M of HNO₃

The absolute uncertainty of multiplication is the sum of relative uncertainty, thus:

ΔM = 0,6527M× (0,0007/0,9585 + 0,001/105,988 + 0,05/27,71) =

0,6527 M× 2,54×10⁻³ = 1,7×10⁻³ M

Thus, molarity of HNO₃ solution and its absolute uncertainty is:

(0,653±0,002) M of HNO₃

I hope it helps!

5 0

3 years ago

An environmental study of a certain metropolitan region indicates that given population x (in thousands), the average daily leve

Vedmedyk [2.9K]

Answer:

In 4 years the carbon monoxide level reach 7.8 parts per million.

Explanation:

The average daily level of carbon monoxide in the air is given by :

$c(x) = 0.5x + 2$ parts per million..[1]

The population of the region after t years is modeled by the formula :

$x(t) = 10 + 0.1t^2$ ...[2]

If level of carbon monoxide level reach 7.8 parts per million in t years.

Using [1] to calculate value of x.

c(x)= 7.8 parts per million

c(x) = 0.5x + 2 parts per million

7.8 parts per million = (0.5x + 2 ) parts per million

Solving for x , we get ;

x = 11.6

Using [2] to calculate value of t.:

x(t) = 11.6

$11.6 = 10 + 0.1t^2$

Solving for 't' we get ;

t = 4 years

In 4 years the carbon monoxide level reach 7.8 parts per million.

3 0

3 years ago

Unit 2 Test

Dafna11 [192]

Answer:

the answer to this question is producer

3 0

2 years ago

Energy is the ability to do

Aleonysh [2.5K]

As we all know that energy is the ability to do work

8 0

2 years ago

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