The molecular formula of calcium nitrite is
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Ca2+ has valency 2; nitrite NO2- has valency 1 — criss-cross gives Ca(NO2)2.
The valency of iron in ferric oxide (Fe2O3) is
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'Ferric' always indicates Fe3+. In Fe2O3: 2×v = 3×2, so v=3.
The radicals present in sodium thiosulfate are
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Sodium thiosulfate is Na2S2O3. Na+ valency=1, S2O32- valency=2, so 2 Na+ per 1 S2O32-.
What is the valency of mercury in Hg2Cl2?
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2 Cl- ions give total charge of 2-. Shared across 2 Hg atoms, each Hg has valency 1.
The formula of a certain metal bicarbonate is M(HCO3). What is the formula of its chloride?
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M(HCO3) means M has valency 1 (HCO3- is monovalent). So the chloride is MCl.
The valency of Mn in MnO2 and P in PH3 is respectively
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In MnO2: Mn + 2×(-2)=0 so Mn=+4, valency=4. In PH3: P+3(+1)=0 so P=-3, valency=3.
Which pair of formulae is correct? (Ag/NH4/K/Zn set)
Ag+ valency 1: AgHCO3 correct. K+ valency 1: K3PO4 correct (PO43- valency 3).
The formula of a metal sulphate is M2SO4. What is the formula of the metal nitrate?
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M2SO4 means M has valency 1 (SO42- valency=2, so 2M). NO3- is monovalent, so formula = MNO3.
The molecular formulas of silver chloride; ferrous carbonate; and cupric nitrate are respectively
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Ag+=1, Cl-=1 → AgCl. Fe2+(ferrous)+CO32-=FeCO3. Cu2+(cupric)+NO3-=Cu(NO3)2.
A and B atoms have 2 and 6 valence electrons respectively. The compound that A and B are most likely to form is
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A (2 valence e) loses 2e to become A2+. B (6 valence e) gains 2e to become B2-. They combine in 1:1 ratio.
The formulas of sodium hypochlorite; potassium thiosulfate; and sodium dichromate are respectively
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Hypochlorite=ClO-, Thiosulfate=S2O32-, Dichromate=Cr2O72-. Na and K are monovalent.
The molecular formula of silver chromate is
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Ag+ has valency 1; chromate CrO42- has valency 2 — criss-cross gives Ag2CrO4.
The molecular formulas of sodium bicarbonate; sodium carbonate; magnesium nitrite; and magnesium nitrate are respectively
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Na is monovalent. Mg is divalent. Bicarbonate=HCO3-, Carbonate=CO32-, Nitrite=NO2-, Nitrate=NO3-.
Which pair of formulae is correct?
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NH4+ valency 1: NH4HCO3 correct. K+ valency 1 and SO42- valency 2: K2SO4 correct.
