BMAT 2019-S2

Explanation

The correct answer is E.

This is a typical genetic engineering question which can be answered mostly through elimination.

W (the grey rectangle) is a small section of the chromosome shown in the picture – this is known as a gene. Hence, we can eliminate options A-D. 

X appears two times in the picture and both times it is involved with cutting. This should indicate to you that X is a restriction enzyme. It is first used to cut the gene out of the chromosome and then the same enzyme used to cut the same section out of the plasmid. We are now down to options E and G which are only differentiated by Y.

Y is a plasmid as opposed to a bacterium. A plasmid is a circular strand of DNA present within the bacterium. It is the plasmid that gets cut by the restriction enzyme NOT the bacterium.

Z is seen to be sticking the gene taken out of the chromosome and the plasmid together. This indicates that Z is a DNA ligase which is the gluing enzyme.

Explanation

The correct answer is C.

The first thing that you should notice is that CaCO3 is a metal carbonate. This should make you think of the general equation: metal carbonate + acid -> metal salt + water + carbon dioxide. The question states that when the cleaning solution is applied, there is effervescence (fizzing) which coincides with the release of carbon dioxide gas seen in the equation. 

Hence, we can be confident that the cleaning solution is acidic which means that Option 1 is true.

The gas release, as mentioned earlier, is carbon dioxide gas NOT hydrogen so Option 2 is incorrect.

This is a neutralisation reaction as CaCO3 is a base (alkaline) and the cleaning solution is acidic. This means that as the reaction progresses, the pH gets closer to neutral i.e. the pH decreases as originally because of the presence of the base, the pH was high.  Therefore, Option 3 is incorrect.

Finally, although we don’t know what salt is produced at the end of the reaction, it says in the question that the solid limescale disappears.

This suggests that it is being converted into a more soluble salt. Hence, Option 4 is correct.

Explanation

The correct answer is B.

We are given the values for mass and acceleration in the question which enables us to use the formula F=ma to calculate the resultant force of the cyclist. Remember that resultant force is the overall/net force of the cyclist

The resultant force is therefore 50 x 4 = 200N

Taking the direction the cyclist is travelling in as positive, we can then set up an equation where:  Forward force produced by the cyclist and the bicycle (600N) – Resistive forces acting against the cyclist and bicycle (300N) – Air resistance = 200N

600 – 300 – Air resistance = 200

Air resistance therefore = 100N, so B is the correct answer

Explanation

The correct answer is B.

The first thing to do is simplify the equation given in the question p + q = 3(p – q) can be written as p + q = 3p – 3q 

This can then be rearranged to 4q = 2p

Both sides can then be divided by 2 to simplify further to get p = 2q

We can now substitute the expression p = 2q into the equation the question is asking us to solve. Everytime p appears in this equation, we can simply replace this with 2q.

Numerator: 2q x q =2q²

Denominator (2q)² + q² = 4q² + q² = 5q²

Putting it all together: 2q²/5q² can then be simplified to ⅖

Explanation

The correct answer is A.

The question states that ‘the shaded areas represent processes that can happen without the use of energy provided by cellular respiration.’

This means that the processes within the shaded areas do not require ATP and are therefore passive processes. 

Looking at the answer options, the processes mentioned in the table are active transport, diffusion, osmosis and aerobic respiration. We can sort these processes out into whether they require ATP or not as this will guide us towards the answer

Area 1 is unshaded which suggests that the processes in this area are active i.e. require ATP. This means that active transport and aerobic respiration are the only processes that can be in Area 1. From this we can eliminate options C, D and E.

Areas 2 and 3 are shaded so the processes in these areas do not require ATP. This means that Areas 2 and 3 can contain diffusion and osmosis. From this we can eliminate options B, F and G. Therefore, A is the correct answer.

Explanation

The correct answer is D.

During electrolysis, positive ions move towards the cathode (the negative electrode) and get reduced i.e. they GAIN electrons. The question states that the chemist wants to electroplate a copper rod with a layer of silver – this means that silver is being deposited on the copper rod. 

Therefore one of the half equations must result in the formation of silver atoms from their ions i.e. Ag+ + e- -> Ag

This is a reduction reaction so it will be happening at the cathode. This suggests that the cathode will be made of copper. Hence, we can eliminate options B, C and E.

The positive silver ions must therefore be coming from the anode which is therefore made of silver. The silver anode undergoes an oxidation reaction i.e. they LOSE electrons 

Ag -> Ag+ + e-

We are now down to options A and D which are differentiated by the electrolyte. In electroplating, the electrolyte should be an aqueous solution of the coating metal. Therefore the electrolyte should be silver nitrate solution which makes option D the correct one.

Explanation

The correct answer is C.

The formula for density is mass/volume

We can calculate the mass of the object X by finding the difference between the two values shown on the weighing scale. The mass of object X is therefore 950g – 750g = 200g

In a similar way, we can also find the volume of X. The value on the measuring cylinder when X has been lowered into the liquid is 500cm³.

The original level of the measuring cylinder was 375cm³. Therefore the volume of X is 500cm³ – 375cm³ = 125cm³

Inputting these values into the density formula, the density of X is 200/125 which is 1.6gcm-³

Explanation

The correct answer is C.

The first thing to do is get rid of the standard form and write out the fraction as you normally would

After this, rewrite the fraction in terms of square numbers as these can then be easily square rooted. Remember that square rooting a fraction means multiplying each of the indices by a half. The fraction can then be simplified – note that when dividing indices, you simply subtract the indices from each other. 

Explanation

The correct answer is D.

Statement 1 suggests an inverse relationship between the respiration rate of the lizard and the environmental temperature i.e. that the respiration rate increases as the temperature drops from 25 degrees to 10 degrees. This is INCORRECT. We can see that the carbon dioxide concentration decreases as the temperature decreases – suggesting that the respiration rate of the lizard is decreasing. This is indicative of a directly proportional relationship NOT an inverse one.

Statement 2 is incorrect as we do not have enough information to conclude that the lizard is only respiring aerobically

Statement 3 is correct as the chemical test for the presence of carbon dioxide is by bubbling it through limewater.

Explanation

The correct answer is H.

This question requires knowledge about the properties of Group 1 metals but can also be largely worked out through common sense. As you go down the group, the outer shell electrons are further away from the positively charged nucleus, experience more shielding and are subsequently less attracted to the nucleus and easier to lose. This means that the Group 1 metal with the largest atomic number (which is right at the bottom of the group) is the most reactive of them and thus the most easily oxidised (loses its outer electron the most readily). Thus, Statements 1 and 3 are correct. Statement 2 is also correct as all the Group 1 metals have one electron in their outer shell (outer shell is the same thing as the highest occupied energy level mentioned in the question).

Explanation

The correct answer is C.

The question states that the larger sphere is negatively charged. This would suggest that there are fewer protons than electrons in the larger sphere to give an overall negative charge. Hence we can eliminate options D, E and F.

As electrons in the smaller sphere are repelled from the larger sphere and flow into the earth, the smaller sphere loses electrons. This will give it an overall positive charge. Therefore the correct option is C.

Explanation

The correct answer is H.

The general formula for working out a gradient is as follows. As we are told the co-ordinates for M and N, and the gradient, we can form an equation by substituting the coordinate values into the equation below.

Substitution of the coordinates looks like this:

We have now worked out that p = -2.

The point r is the y-intercept of the equation of the line

So using the format y = mx + c, the equation of the line is y = -3x + r

We can now input the actual co-ordinates for point M into y = -3x + r to find out the value of R

Having worked out that p = -2, the coordinates of M are (6, -7)

Therefore, -7 = -18 + r

r therefore = 11

Explanation

The correct answer is H.

Amino acids, Cellulose and Lipids all contain carbon and are ingested by other organisms. Hence they all make up part of the carbon cycle.

Explanation

The correct answer is A.

Comparing curve Y to curve X, the first thing that is noticeable is that Y has a steeper gradient to begin with, which implies a higher rate of reaction. This would suggest that the manganese(IV) oxide particle size is smaller in reaction Y i.e. it is a powder (as a high surface area gives rise to a higher rate of reaction). We can therefore eliminate options D and E. 

The next thing to notice is that curve Y plateaus at a lower level than curve X. By counting the number of squares on the y axis we can work out how much gas is produced by reactions X and Y. Reaction X produced 5 squares worth of gas, whereas reaction Y only produces 4 i.e. Reaction Y produces ⅘ the amount of gas. 

This would suggest that reaction Y uses ⅘ the amount of hydrogen peroxide compared to reaction X. Using the formula number of moles = concentration x volume, the number of moles of hydrogen peroxide used in Reaction X was 0.1 x 50/1000 = 0.005 mol. ⅘ of this amount is 0.004mol which is the number of moles of hydrogen peroxide used in Reaction Y. 

We can then look at the remaining answer options A, B and C to see which two values multiply together to give 0.004. This shows that A is the correct answer.

Explanation

The correct answer is F.

A is incorrect as longitudinal waves can travel at different speeds.

B is incorrect as it is transverse waves NOT longitudinal that cause vibrations perpendicular to the direction of energy transfer. 

C is incorrect as sound waves are longitudinal

D is incorrect as in certain conditions, longitudinal waves can travel faster than transverse waves.

E is incorrect as all electromagnetic waves are transverse waves but this does not mean that all transverse waves are electromagnetic

F is correct as ultrasonic waves are a type of sound wave which are longitudinal

G is incorrect as ultraviolet waves are transverse waves so do not consist of compressions and rarefactions. Only longitudinal waves consist of these.

H is incorrect as X-rays can travel in a vacuum. All waves in the electromagnetic spectrum (transverse) can travel in a vacuum.

Explanation

The correct answer is D.

We can draw the rectangle out as below

The area of the rectangle is 66cm². So we can form the equation x(7-√5) = 66 and then rearrange it so that x is made the subject. As we have a surd in the denominator, we must rationalise which is why the numerator and denominator have both been multiplied by 7+√5. After this, there is some simplification of the fraction as 66 and 44 are both divisible by 22. We finally end up with a simplified expression for x. 

The next thing is to work out the perimeter of the triangle. 

This can be written as 2x + 2(7-√5)

As we now know the value for x, this is easy to do: 2x = 21 + 3√5

Therefore, perimeter = 21 + 3√5 + 14 – 2√5 which can then be simplified to 35 + √5, hence D is the correct answer.

Note that this is quite a time-consuming question so if you do notice you’re spending upwards of a minute and a half on this question and not nearing the answer, you may want to consider guessing and moving on.

Explanation

The correct answer is D.

The question states that the pea plant is heterozygous for seed colour which means that it has the genotype Yy. It also states the plant is homozygous for seed shape which means that it can either have the genotype RR or rr. 

Statement 1 is incorrect as the plant cannot have both R and r alleles. It can only have one or the other.

Statement 2 could be correct.

Statement 3 is incorrect for the same reason as Statement 1.

Statement 4 is correct.

Statement 5 is incorrect as it is showing a homozygous genotype when the question states that seed colour is heterozygous.

Statement 6 is incorrect as it is showing a heterozygous genotype when the question states that seed shape is homozygous.

Statement 7 could be correct.

Explanation

The correct answer is E.

The ionic equation shows that one mole of MnO4– ions reacts with 5 moles of Fe²+ ions.

Using the formula number of moles = concentration x volume, we can work out the number of moles of MnO4– ions that reacted with the iron ions.

Remember that volume in the formula is measured in dm³ so we must remember to convert

Moles of MnO4– ions = 10/1000 x 0.05 = 0.01 x 0.05 = 0.0005 mol = 5 x 10-4 mol

Therefore, the moles of Fe²+ ions is five times this amount = 2.5 x 10-³ mol

To work out the concentration = number of moles/volume. Convert both values to standard form to make the calculation easier. 

Concentration of Fe²+ ions = 2.5 x 10-³/2.5 x 10-² = 1 x 10-1 mol dm-³

Explanation

The correct answer is A.

The question states that the expansion has caused a change in EM radiation from gamma rays to microwaves. From your knowledge of the properties of EM waves, you should know that microwaves have a longer wavelength and lower frequency than gamma rays. Hence statements 1 and 2 are incorrect. Statement 3 is also incorrect as wavelength and frequency are always inversely proportional to each other.

Explanation

The correct answer is E.

With probability questions like these, it is always useful to draw out a tree diagram.

The question contains the words ‘given that’ and so you should recall the ‘given that’ formula:

The formula shows that the probability of event B happening given event A is equivalent to the probability of event A and event B divided by the probability of event A.

In this case, event A is Sylvia catching the train which is ‘given’ and event B is the bus being on time.

P(Bus on time | Catches the train) = (0.6 x 0.8)/((0.6×0.8) + (0.4 x 0.6))

= 0.48/0.48 + 0.24

= 0.48/0.72

= ⅔

Explanation

The correct answer is B.

Statement 1 is correct as 3 base pairs code for 1 amino acid. Therefore 500 base pairs code for 166 amino acids as a maximum.

Statement 2 is incorrect as mature red blood cells do not have a nucleus and therefore do not have any chromosomes.

Statement 3 is incorrect as adenine is complementary to thymine so we would expect the same number of bases of adenine as thymine. This does not necessarily mean that guanine will have the same number of bases.

Explanation

The correct answer is D.

The question states that the vapour is an alkane which has the general formula CnH2n+2. As a result we are able to eliminate options A and C. Due to Avogadro’s Law which states that: 1 mole of every gas occupies the same volume, we can see that the carbon dioxide is being produced in a 3:1 ratio to the alkane vapour (as 105 = 35 x 3). Thus, for every molecule of alkane that is combusted, 3 molecules of carbon dioxide gas are produced. Therefore in terms of the molecular formula of the alkane, the number of carbons must be a multiple of 3 and hence option D is correct.

Explanation

The correct answer is A.

The formula for momentum = mass x velocity

The mass is 400kg and the velocity is 15ms–¹

 400 x 15 = 6000kg ms–¹

The formula which connects momentum and force is force = change in momentum/time

The initial momentum of the water we take to be 0 so the change in momentum is equivalent to 6000kg ms–¹.

Using the formula, the force is therefore 6000/12 = 500N

Since there are two nozzles on one jetpack, the total force exerted is 500 x 2 = 1000N

Explanation

The correct answer is H.

First, you must recall that the interior angle of a pentagon is 108 degrees.

The diagram below shows the bearing of 110 degrees at the start of the third leg. Focussing on this point and taking into account the interior angle, we can work out the angle marked in red is 142 degrees (360 – 110 – 108 = 142)

Due to the supplementary angles rule, we can work out the bearing of the second leg which is simply 180 -142 = 38 degrees.

Using the supplementary angles rule again, we can get the angle of 34 degrees (180 – (38 + 108) = 34)

Then to work out the bearing of the first leg it is 360 – 34 = 326 degrees.

Explanation

The correct answer is B.

In the normal ultrafiltration process, large protein molecules should be unable to pass from the blood vessels into the Bowman’s capsule. There should be no protein in the ultrafiltrate. If there is protein in the urine, this is suggestive of a problem with the ultrafiltration process as nothing else could cause this. Hence Statement 1 is correct because if there is damage to cell membranes between the blood vessels and the Bowman’s capsule, this may mean that large proteins could pass through these damaged membranes into the capsule. 

Statement 2 and 3 are both incorrect as they have no relevance to the ultrafiltration process.

Explanation

The correct answer is E.

Diborane molecules with a RMM of 26 are made up of two ¹ºB atoms (as well as 6 hydrogen atoms). The probability of this molecule forming based off the abundance of the isotopes given in the question is 0.2 x 0.2 = 0.04

Diborane molecules with a RMM of 27 are made up of one ¹ºB atom and one ¹¹B atom. Note that there are TWO combinations of these because you can get ¹ºB¹¹BH6 AND  ¹¹B¹ºBH6 . So the subsequent probability must be multiplied by two. The probability of this molecule forming is 2 x 0.2 x 0.8 = 0.32

Diborane molecules with a RMM of 28 are made up of two ¹¹B atoms. The probability of this molecule forming is 0.8 x 0.8 = 0.64

We can then create a ratio using these three probabilities 

0.04 : 0.32 : 0.64

This can be simplified to 1: 8: 16

Explanation

The correct answer is B.

This question incorporates all the formulae related to transformers. 

The first formula to use involves the number of turns on the coils and voltage:

We will represent voltage out as x

x/240 = 100/400

x = 60 V

Thus, we can eliminate options E, F, G and H

As the transformer is 100% efficient we can use the equation VpIp = VsIs to work out the input current. We will represent input current as y.

240 x y = 60 x 2

y = 0.5 A 

We can further eliminate options C and D

Finally to work out output power, we use P = IV using the values for output voltage and current 

Power = 2 x 60 = 120W

Therefore, the correct answer is B.