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Elis [28]
3 years ago
6

Why is a control needed in a valid experiment?

Chemistry
1 answer:
aliina [53]3 years ago
5 0
You need a control so you have something to compare the experimental group on-- If you don't have a control group, how will you know what's changed?
You might be interested in
Atomic mass unit is calculated with reference to
Gennadij [26K]
An atomic mass unit is defined as a mass equal to one twelfth the mass of an atom of carbon-12. The mass of any isotope of any element is expressed in relation to the carbon-12 standard. For example, one atom of helium-4 has a mass of 4.0026 amu. An atom of sulfur-32 has a mass of 31.972 amu.
8 0
3 years ago
Read 2 more answers
S-2-iodooctane lost his opticaly activity in soln on tratment wwithNaI. Explain
IceJOKER [234]

Answer:

Repeated SN2 reactions occur leading to the formation of a racemic mixture

Explanation:

S-2-iodooctane is a chiral alkyl halide with an asymmetric carbon atom. The presence of an asymmetric carbon atom implies that it can rotate plane polarized light and thus lead to optical isomerism. The two configurations of the compound are R/S according to the Cahn-Prelong-Ingold system.

However, when S-2-iodooctane is treated with sodium iodide in acetone, repeated SN2 reactions occur since the iodide ion is both a good nucleophile and a good leaving group. Hence a racemic modification is formed in the system with time hence we end up with (±)- Iodooctane.

5 0
3 years ago
If the velocity of a wave is 12 m/s and its frequency is 600 hertz, what would be its wavelength?
Black_prince [1.1K]

Answer:

<em>»</em><em> </em><em>λ </em><em>=</em><em> </em><em>0</em><em>.</em><em>0</em><em>2</em><em>m</em>

Explanation:

Given :

Velocity of the wave {v}= 12 m/s

Frequency {f} = 600 Hz

Apply Wavelength formula :

• λ =  \frac{v}{f}

→ λ = \frac{12}{600}

→ λ = \frac{1}{50}

→ λ = 0.02m

3 0
2 years ago
Read 2 more answers
A 100.0-mL sample of 1.00 M NaOH is mixed with 50.0 mL of 1.00 M H2SO4 in a large Styrofoam coffee cup calorimeter fitted with a
worty [1.4K]

Answer:

THE ENTHALPY CHANGE IN KJ/MOLE IS +114 KJ/MOLE.

Explanation:

Heat = mass * specific heat capacity * temperature rise

Total volume = 100 + 50 = 150 mL

Total mass = density * volume

Total mass = 1 * 150 mL = 150 g

So therefore, the heat evolved during the reaction is:

Heat = 150 * 4.18 * ( 31.4 - 22.3)

Heat = 150 * 4.18 * 9.1

Heat = 5705.7 J

Equation for the reaction:

2 NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2 H2O(l)  

From the equation, 2 moles of NaOH reacts with 1 mole of H2SO4 to produce 1 mole of Na2SO4 and 2 moles of water

50 mL of 1 M of H2SO4 contains

50 * 1 / 1000 mole of acid

= 0.05 mole of acid

The production of 1 mole of water evolved 5705.7 J of heat and hence the enthalpy changein kJ per mole will be:

0.05 mole of H2SO4 produces 5705.7 J of heat

1 mole of H2SO4 will produce 5705.7 / 0.05 J

= 114,114 J / mole

In kj/mole = 114 kJ/mole.

Hence, the enthalpy change of the reaction in kJ /mole is +114 kJ/mole.

5 0
3 years ago
Assume the recommended single dose of an antihistamine for a child weighing between 18-23 lbs is 0.75 teaspoons (tsp). if 1.00 t
blagie [28]

We are given that 1 teaspoon is equivalent to 5 mL, therefore 0.75 teaspoon is:

0.75 teaspoon * (5 mL / 1 teaspoon) = 3.75 mL

 

So the mass is density times volume:

mass = (12.5 mg/5 ml) * 3.75 mL

<span>mass = 9.375 mg</span>

7 0
3 years ago
Read 2 more answers
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