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Which of the bromine oxoanion species does NOT undergo disproportionation?
Disproportionation occurs when an element in an intermediate oxidation state simultaneously undergoes oxidation and reduction.
- $\text{BrO}^-$ (Br = +1): can disproportionate to Br$^-$ ($-1$) and BrO$_3^-$ ($+5$) ✓
- $\text{BrO}_2^-$ (Br = +3): can disproportionate to $\text{BrO}^-$ and $\text{BrO}_3^-$ ✓
- $\text{BrO}_3^-$ (Br = +5): can disproportionate under certain conditions ✓
- $\text{BrO}_4^-$ (Br = +7): Br is in its highest oxidation state for bromine — it cannot be further oxidised, so disproportionation is not possible.
$\text{BrO}_4^-$ does not undergo disproportionation.
The genetic material of which virus is enclosed by a lipid membrane (envelope)?
Influenza virus is an enveloped virus (lipid bilayer derived from host cell). Enterovirus, Hepatitis A, and Polio are non-enveloped (naked) picornaviruses.
Let $[x]$ denote the greatest integer $\leq x$. Find: $\displaystyle\lim_{x\to0}\dfrac{\tan(\pi\sin^2 x)+(|x|-\sin(x[x]))^2}{x^2}$
Split into right and left limits.
Right limit ($x\to0^+$): $[x]=0$, so $\sin(x[x])=0$, $|x|=x$.
$\dfrac{\tan(\pi\sin^2x)+x^2}{x^2}$. Using $\tan(\pi\sin^2x)\approx\pi\sin^2x\approx\pi x^2$:
$=\pi+1$
Left limit ($x\to0^-$): $[x]=-1$, $\sin(x[x])=\sin(-x)=-\sin x$, $|x|=-x$.
$=\dfrac{\tan(\pi\sin^2x)+(-x-(-\sin x))^2}{x^2}=\dfrac{\pi x^2+(\sin x-x)^2}{x^2}\to\pi+0=\pi$
Left $\neq$ Right, so the limit does not exist.
Which philosopher wrote the 'Two Treatises of Government'?
John Locke's work argued against absolute monarchy and for consent of the governed.
Using the Principle of Calorimetry: Heat lost by metal = Heat gained by (water + calorimeter).
$m_m s_m (100 - 21.5) = (m_w s_w + m_c s_c) (21.5 - 8.4)$
$0.192 \times s_m \times 78.5 = (0.24 \times 4184 + 0.128 \times 394) \times 13.1$
$15.072 s_m = (1004.16 + 50.432) \times 13.1 = 1054.592 \times 13.1 = 13815.15$
$s_m \approx 916.6 \text{ J kg}^{-1}\text{K}^{-1}$
Using the table below, compare the dollar values of the two foreign currencies:
| Country | Value of 1 US Dollar |
|---|---|
| Argentina | 0.93 peso |
| Kenya | 32.08 shillings |
Quantity A: The dollar value of 1 Argentine peso
Quantity B: The dollar value of 1 Kenyan shilling
If $1$ USD $= 0.93$ peso, then $1$ peso $= \dfrac{1}{0.93} \approx 1.075$ USD.
If $1$ USD $= 32.08$ shillings, then $1$ shilling $= \dfrac{1}{32.08} \approx 0.031$ USD.
Quantity A $\approx 1.075$ USD > Quantity B $\approx 0.031$ USD.
Quantity A is greater.
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