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Zanzabum
3 years ago
15

Student perfotms a Benedict's test on an unknown substance. He adds reagent(the chemical required to make a color change), and n

othing happens. What can you conclude?
Chemistry
1 answer:
elixir [45]3 years ago
7 0

Answer:

Reducing sugars are absent

Explanation:

Benedict's solution is an substance used in testing sugars. It is mixture of sodium carbonate, sodium citrate and copper(II) sulfate pentahydrate. It can be used instead of Fehling's solution in testing for the presence of reducing sugars.

Reducing sugars contain the -CHO group. If there is no colour change after the addition of Benedict's solution, then we can conclude that reducing sugars are absent.

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How many grams of H2O are produced when 5.38g of O2 is reacted?
dolphi86 [110]

Answer:

2.33 g H20

Explanation:

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2 years ago
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Duncan knows that it takes 36400 cal of energy to heat a pint of water from room temperature to boiling. However, Duncan has pre
brilliants [131]

Answer:

\large \boxed{\text{122 000 J}}

Explanation:

1. Calculate the energy needed

\text{Energy} = \text{0.800 pt} \times \dfrac{\text{36 400 cal}}{\text{1 pt}}  = \text{ 29 120 cal}

2. Convert calories to joules

\text{Energy} = \text{29 120 cal} \times \dfrac{\text{4.184 J}}{\text{1 cal}} = \textbf{122 000 J}\\\\\text{The water will have absorbed $\large \boxed{\textbf{122 000 J}}$}

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3 years ago
What's the name of the part of cells that sense molecules and other cells?
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Because membrane receptors interact with both extracellular signals and molecules within the cell, they permit signaling molecules to affect cell function without actually entering the cell.
6 0
3 years ago
1. Define the unit 'mole'
serious [3.7K]

Answer:

Below

Explanation:

The mole, symbol mol, is the SI base unit of amount of substance. The quantity amount of substance is a measure of how many elementary entities of a given substance are in an object or sample

7 0
2 years ago
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Air containing 0.06% carbon dioxide is pumped into a room whose volume is 12,000 ft3. The air is pumped in at a rate of 3,000 ft
castortr0y [4]

Answer:

A(t)=1.8+34.2*e^{-t}

Explanation:

The concentration of CO2 in the room will be the amount of CO2 in the room at time t, divided by the volume of the room.

Let A(t) be the amount of CO2 in the room, in ft3 CO2.

The air entering the room is 3000 ft3/min with 0.06% concentrarion of CO2. That can be expressed as (3000*0.06/100)=1.8 ft3 CO2/min.

The mixture leaves at 3000 ft3/min but with concentration A(t)/V. We can express the amount of CO2 leaving the room at any time is A(t).

We can write this as a differential equation

dA/dt=v_i-v_o=1.8-A

We can rearrange and integrate

dA/dt=v_i-v_o=1.8-A\\\\dA/(A-1.8)=-dt\\\\\int(dA/(A-1.8) = -\int dt\\\\ln(A-1.8)=-t+C\\\\A-1.8=e^{-t}* e^{C}=C*e^{-t}\\\\A=1.8+C*e^{-t}

We also know that A(0) = 12000*(0.3/100)=36 ft3 CO2.

A(0)=1.8+C*e^{-0}\\36=1.8+C*1\\C=34.2

Then we have the amount A(t) as

A(t)=1.8+34.2*e^{-t}

5 0
3 years ago
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