All practice questions

In an industrial chlor-alkali membrane cell, concentrated sodium chloride solution (brine) is electrolyzed using a constant current of $19.3\text{ A}$ for $50\text{ minutes}$. What is the mass, in grams, of sodium hydroxide ($\text{NaOH}$) produced in the solution? [Molar mass of $\text{NaOH} = 40.0\text{ g mol}^{-1}$, Faraday constant $F = 96,500\text{ C mol}^{-1}$]

A $16.1\text{ g}$ sample of hydrated sodium tetraoxosulfate(VI), $\text{Na}_2\text{SO}_4 \cdot x\text{H}_2\text{O}$, is heated in a crucible until all the water of crystallization is driven off. The mass of the remaining anhydrous salt is $7.1\text{ g}$. Calculate the value of $x$. [Relative atomic masses: $\text{Na} = 23$, $\text{S} = 32$, $\text{O} = 16$, $\text{H} = 1$]

In an industrial electroplating plant, a steel component is coated with silver in an electrolytic bath. If a constant electric current of $2.0\text{ A}$ is passed through the bath for $48.25\text{ minutes}$, what is the mass of silver, in grams, deposited on the cathode? [Molar mass of $\text{Ag} = 108\text{ g mol}^{-1}$, $1\text{ F} = 96500\text{ C mol}^{-1}$]

In sweet pea plants (*Lathyrus odoratus*), purple flower color ($P$) is dominant over red flower color ($p$), and long pollen grain ($L$) is dominant over round pollen grain ($l$). If a heterozygous dihybrid plant with the genotype $PpLl$ is self-pollinated and yields a total of $160$ F2 seeds, how many of these seeds are expected to produce plants with the double recessive phenotype of red flowers and round pollen grains?

A steady electric current of $5.0\text{ A}$ is passed through molten lead(II) bromide ($PbBr_2$) for $32\text{ minutes}$ and $10\text{ seconds}$. What mass of lead, in grams, is deposited at the cathode? [$\text{Pb} = 207$, $1\text{ F} = 96\text{ }500\text{ C mol}^{-1}$]

In humans, Duchenne muscular dystrophy is inherited as an X-linked recessive disorder ($X^d$), while the normal allele is dominant ($X^D$). A phenotypically normal woman seeks genetic counseling. Her maternal grandfather had Duchenne muscular dystrophy, whereas her maternal grandmother was homozygous normal. Her father is phenotypically normal. If this woman marries a phenotypically normal man, what is the probability (expressed as a percentage) that their first male child will be affected by the disorder?

In humans, red-green color blindness is an X-linked recessive trait ($X^c$), whereas normal vision is controlled by the dominant allele ($X^C$). Albinism is an autosomal recessive disorder ($a$), whereas normal skin pigmentation is controlled by the dominant allele ($A$). A woman with normal vision and normal skin pigmentation, whose father was both color-blind and albino, marries a man with normal vision who is a carrier for albinism. If this couple produces a male child (son), what is the percentage probability that the son will be both color-blind and albino?

During an ecological study of an agricultural fish pond in Ibadan, Oyo State, a student employed the mark-release-recapture technique to estimate the population size of tilapia (*Oreochromis niloticus*). In the initial sampling, $120$ fish were captured, marked with harmless plastic tags, and released back into the pond. Two days later, a second sample of $150$ fish was netted, out of which $30$ individuals were found to be marked. What is the estimated total population size of tilapia fish in the pond?

In guinea pigs (*Cavia porcellus*), black coat color ($B$) is dominant over white coat color ($b$), and short hair ($S$) is dominant over long hair ($s$). If a heterozygous black, short-haired guinea pig ($BbSs$) is mated with a white, long-haired guinea pig ($bbss$) and they produce a total of 640 offspring, how many of the offspring are expected to display a black coat and long hair?

What is the molar concentration (in $\text{mol dm}^{-3}$) of a tetraoxosulfate(VI) acid solution if $20.0\text{ cm}^3$ of the acid is required to completely neutralize $25.0\text{ cm}^3$ of a $0.08\text{ mol dm}^{-3}$ sodium hydroxide solution?

An ecology student sampled the population of guinea grass (*Panicum maximum*) in a $600\text{ m}^2$ pasture plot in Kaiama, Kwara State, using a $0.5\text{ m} \times 0.5\text{ m}$ quadrat frame. The counts of grass clumps recorded from 10 randomly placed quadrats were 4, 6, 3, 7, 5, 2, 8, 4, 6, and 5. What is the estimated total population of guinea grass clumps in the entire pasture plot?

An ecological survey was conducted in the Borgu sector of Kainji Lake National Park to estimate the population size of grasscutters (*Thryonomys swinderianus*). In the initial phase, $80$ grasscutters were captured, marked with ear tags, and released back into the habitat. One week later, a second sample of $100$ grasscutters was captured, out of which $20$ individuals retained their mark. If post-marking field monitoring established that $10\%$ of all originally marked animals lost their tags during the interval, what is the estimated total population size of grasscutters in the study area?

A subatomic particle of mass $6.63 \times 10^{-31}\text{ kg}$ moves with a velocity of $1.0 \times 10^6\text{ m/s}$. Calculate its de Broglie wavelength in nanometers ($\text{nm}$). (Take Planck's constant $h = 6.63 \times 10^{-34}\text{ J}\cdot\text{s}$ and $1\text{ nm} = 10^{-9}\text{ m}$)