Sorry, that is incorrect.

The only correct answer is: free radical substitution.

• electrophilic addition is not correct because electrophilic addition would be the reaction mechanism between alkenes, such as ethene, and chlorine but the substance in the question is the alkane, ethane
• electrophilic substitution is not correct because electrophilic substitution involves the reactions of aromatic systems but this question refers to the reaction of the alkane, ethane
• free radical addition is not correct because the mechanism of reaction between an alkane such as ethane and chlorine involves substitution and not addition

Sorry, that is incorrect.

The only correct answer is: no change

• orange to green is not correct because tertiary alcohol is not oxidized
• green to orange is not correct because this is an incorrect colour change for acidified dichromate
• purple to colourless is not correct because this is an incorrect colour change for these reagents.

Sorry, that is incorrect.

The only correct answer is: 3

Sorry, that is incorrect.

The only correct answer is: 8 protons, 10 neutrons, and 8 electrons

• 9 protons, 9 neutrons, and 9 electrons is incorrect because oxygen atoms do not have this number of protons.
• 0 protons, 8 neutrons, and 10 electrons is incorrect because oxygen atoms do not have this number of protons.
• 18 protons, 18 neutrons, and 18 electrons is incorrect because oxygen atoms do not have this number of protons.

Sorry, that is incorrect.

The only correct answer is: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^{6}$

• $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}$ is incorrect because this is the electronic configuration of $^{33}As^{3+}$
• $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^{3}$ is incorrect because this is the electronic configuration of $^{33}As$
• $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^{3}4d^{3}$ is incorrect because this has added electrons in the $4d$ orbital.

Sorry, that is incorrect.

The only correct answer is: 801 , 2,427 , 3,660 , 25,026 , 32,828

• 738 , 1,451 , 7,733 , 10,541 , 13,629 is incorrect because it is typical of group 2 elements.
• 1,086 , 2,353 , 4,621 , 6,223 , 37 832 is incorrect because it is typical of group 4 elements.
• 1,402 , 2,856 , 4,578 , 7,475 , 9 445 is incorrect because it could be for group 5,6,7,8 or transition elements.

Sorry, that is incorrect.

The only correct answer is: $Mn^{2+}$

• $Cr^{3+}$ is incorrect because it is $3d^{3}$ not $3d^{5}$
• $Fe^{2+}$ is incorrect because it is $3d^{6}$ not $3d^{5}$
• $Mn^{3+}$ is incorrect because it is $3d^{4}$ not $3d^{5}$

Sorry, that is incorrect.

The only correct answer is: $CO_{2}$

• $H_{2}S$ is not correct because it has a similar shape to water.
• $SO_{2}$ is not correct because it has a trigonal planar shape, resulting from the lone pair and two groups of electrons in the two double bonds.
• $CH_{2} = CH_{2}$ is not correct because it is planar but not linear.

Sorry, that is incorrect.

The only correct answer is: All at 120$^\circ$

• 90$^\circ$ and 109.5$^\circ$ is not correct because the angles within a layer of graphite and graphene are neither 90$^\circ$ nor 109.5$^\circ$ but are all 120$^\circ$
• All at 109.5$^\circ$ is not correct because the angles within a layer of graphite and graphene are not 109.5$^\circ$ but are all 120$^\circ$
• 109.5$^\circ$ and 120$^\circ$ is not correct because there are no angles within a layer of graphite and graphene that are 109.5$^\circ$ but they are all 120$^\circ$

Sorry, that is incorrect.

The only correct answer is: hydrogen bonds

• covalent bonds is incorrect because covalent bonds are within molecules, not between molecules
• ionic bonds is incorrect because there are no ionic bonds
• London forces is incorrect because London forces are not the strongest force