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dimulka [17.4K]
3 years ago
15

Which of the following is NOT true about "yield"? a. The value of the actual yield must be given in order for the percent yield

to be calculated. b. The percent yield is the ratio of the actual yield to the theoretical yield. c. The actual yield may be different from the theoretical yield because reactions do not always go to completion. d. The actual yield may be different from the theoretical yield because insufficient limiting reagent was used.
Chemistry
1 answer:
Snowcat [4.5K]3 years ago
8 0
<span>Which of the following is NOT true about "yield"? a. The value of the actual yield must be given in order for the percent yield to be calculated. b. The percent yield is the ratio of the actual yield to the theoretical yield. c. The actual yield may be different from the theoretical yield because reactions do not always go to completion. d. The actual yield may be different from the theoretical yield because insufficient limiting reagent was used.

The correct answer is:
</span><span> d. The actual yield may be different from the theoretical yield because insufficient limiting reagent was used.</span>
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A student determined that the weight-percent recovery for his isolated caffeine proved to be 1.5%. The student was concerned, ex
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Yes. Percent yield shows how efficient one's method is. If his isolated caffeine proved to be at only 1.5%, compared to least 50% as in many of the previous experiments, the student should be very concerned as it shows that something caused the yield to sharply drop.

6 0
3 years ago
The radioactive isotope of lead, Pb-209, decays at a rate proportional to the amount present at time t and has a half-life of 3.
Marina86 [1]

Answer:

Therefore it will take 7.66 hours for 80% of the lead decay.

Explanation:

The differential equation for decay is

\frac{dA}{dt}= kA

\Rightarrow \frac{dA}{A}=kdt

Integrating both sides

ln A= kt+c₁

\Rightarrow A= e^{kt+c_1}

\Rightarrow A=Ce^{kt}         [e^{c_1}=C]

The initial condition is A(0)= A₀,

\therefore A_0=Ce^{0.k}

\Rightarrow C=A_0

\therefore A=A_0e^{kt}.........(1)

Given that the Pb_{209}  has half life of 3.3 hours.

For half life A=\frac12 A_0 putting this in equation (1)

\frac12A_0=A_0e^{k\times3.3}

\Rightarrow ln(\frac12)= 3.3k     [taking ln both sides, ln \ e^a=a]

\Rightarrow k=\frac{ln \frac12}{3.3}

⇒k= - 0.21

Now A₀= 1 gram, 80%=0.8

and A= (1-0.8)A₀ = (0.2×1) gram = 0.2 gram

Now putting the value of k,A and A₀in the equation (1)

\therefore 0.2=1e^{(-0.21)\times t}

\Rightarrow e^{-0.21t}=0.2

\Rightarrow -0.21t= ln(0. 2)

\Rightarrow t= \frac{ln (0.2)}{-0.21}

⇒ t≈7.66

Therefore it will take 7.66 hours for 80% of the lead decay.

3 0
3 years ago
Suppose that there is an air sample and a water sample, each of the same mass and each with an initial temperature, Tinitial, of
klasskru [66]

Answer:

The air will reach a higher final temperature because its specific heat is lower.

Explanation:

6 0
3 years ago
Read 2 more answers
If 100cm3 of O2 diffused in 4s and 50cm3 of gas Y diffused in 3s. calculate the relative molecular mass of gas X (O=16).
sertanlavr [38]

Answer:

T2/T=√M1√M2

T2=3 T1=4 M1=O2=32

M2=?

4/2=√M2/√32

=1.3

Explanation:

8 0
3 years ago
Chlorine reacts with sodium and with hydrogen.
Sonbull [250]

Answer:

Sodium Chloride has Ionic bond while Hydrogen Chloride has covalent bond.

Explanation:

Na has 11 electrons (2, 8, 1) and need to give away 1 electron to be stable

Cl has 17 electrons ( 2, 8, 7) and needs 1 electron to be stable.

Na transfers 1 electron to CL to form Ionic bond.

While

Hydrogen has 1 electron and shares with Chlorine to be stable.

Covalent bond involves sharing.

3 0
3 years ago
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