Question

1. the correct chemical formula for hexaboron silicide is

◯ b₆si
◯ b₇si

1. the correct chemical formula for manganese carbonate is

◯ mn(co₃)
◯ mn₂(co₃)

1. the correct chemical formula for aluminum sulfide is

◯ al₂s₃
◯ ais

Explanation:

Question 9

Step1: Analyze prefix "hexa-"

"Hexa-" means 6, so there are 6 boron (B) atoms. The compound is hexaboron silicide, so boron (B) and silicon (Si) are the elements. The formula should have 6 B atoms and 1 Si atom (since silicide is Si with -ide suffix, implying 1 atom here for the binary compound). So the formula is \( B_6Si \).

Step2: Compare with options

The first option is \( B_6Si \), the second is \( B_7Si \). So the correct one is \( B_6Si \).

Step1: Determine oxidation states

Manganese carbonate: Manganese (Mn) in carbonate compounds (where carbonate is \( CO_3^{2-} \)) - let's consider common oxidation states. Manganese can have +2, +3, etc. Carbonate is \( -2 \) charge. For a neutral compound, the charge of Mn should balance \( CO_3^{2-} \). If Mn is +2, then \( Mn^{2+} \) and \( CO_3^{2-} \) will form \( MnCO_3 \) (which can be written as \( Mn(CO_3) \) if we consider the formula with parentheses for the polyatomic ion, but actually, the correct formula is \( MnCO_3 \), which is equivalent to \( Mn(CO_3) \) here as the subscript for \( CO_3 \) is 1 when Mn is +2. Wait, the options are \( Mn(CO_3) \) and \( Mn_2(CO_3) \). Let's check charges: \( Mn^{2+} \) and \( CO_3^{2-} \), so 1:1 ratio, so formula is \( MnCO_3 \) or \( Mn(CO_3) \) (if we write the polyatomic ion in parentheses, though usually we don't need parentheses if the subscript is 1, but the option has \( Mn(CO_3) \) which is acceptable for showing the polyatomic ion). The other option is \( Mn_2(CO_3) \), which would imply Mn is +1 (since 2*+1 + (-2) = 0, but Mn is more commonly +2 in carbonates). So \( Mn(CO_3) \) is correct.

Step2: Compare with options

The first option is \( Mn(CO_3) \), second is \( Mn_2(CO_3) \). So the correct one is \( Mn(CO_3) \).

Step1: Determine oxidation states

Aluminum sulfide: Aluminum (Al) has a +3 oxidation state (always +3 in compounds), sulfide (S) has -2 oxidation state. To balance charges: let the formula be \( Al_xS_y \). Then \( 3x - 2y = 0 \) (neutral compound). Solving for x and y: least common multiple of 3 and 2 is 6, so x = 2, y = 3. So formula is \( Al_2S_3 \).

Step2: Compare with options

The first option is \( Al_2S_3 \), second is \( AlS \). So \( Al_2S_3 \) is correct.

Answer:

A. \( B_6Si \) (assuming the first option is A, second is B; if options are labeled differently, adjust accordingly, but based on the options given, the first option \( B_6Si \) is correct)

Question 10