stable equilibrium See equilibrium.
staggered See conformation.
staggered conformation See conformation.
stainless steel A form of *steel
containing at least 11–12% of
chromium, a low percentage of carbon, and often some other elements,
notably nickel and molybdenum.
Stainless steel does not rust or stain
and therefore has a wide variety of
uses in industrial, chemical, and domestic environments. A particularly
successful alloy is the steel known as
18–8, which contains 18% Cr, 8% Ni,
and 0.08% C.
stalactites and stalagmites Accretions of calcium carbonate in
limestone caves. Stalactites are tapering cones or pendants that hang
down from the roofs of caves; stalagmites are upward projections from
the cave Ûoor and tend to be broader
at their bases than stalactites. Both
are formed from drips of water containing calcium hydrogencarbonate
in solution and may take thousands
of years to grow.
standard cell A *voltaic cell, such
as a *Clark cell, or *Weston cell,
used as a standard of e.m.f.
standard electrode An electrode
(a half cell) used in measuring electrode potential. See hydrogen half
cell.
standard electrode potential See
electrode potential.
standard solution A solution of
known concentration for use in volumetric analysis.
standard state A state of a system
used as a reference value in thermodynamic measurements. Standard
states involve a reference value of
pressure (usually one atmosphere,
101.325 kPa) or concentration (usually 1 M). Thermodynamic functions
are designated as ‘standard’ when
they refer to changes in which reactants and products are all in their
standard and their normal physical
state. For example, the standard
molar enthalpy of formation of water
at 298 K is the enthalpy change for
the reaction
H 2 (g) + ½O 2 (g) → H 2 O(l)
∆HŠ 298 = –285.83 kJ mol
–1
. Note the
superscript Š is used to denote standard state and the temperature
should be indicated.
standard temperature and pressure See s.t.p.
stannane See tin(iv) hydride.
stannate A compound formed by
reaction of tin oxides (or hydroxides)
with alkali. Tin oxides are amphoteric (weakly acidic) and react to give
stannate ions. Tin(IV) oxide with
molten alkali gives the stannate(IV)
ion
SnO 2 + 2OH
–
→ SnO 3
2– + H 2 O
In fact, there are various ions present
in which the tin is bound to hydroxide groups, the main one being the
hexahydroxostannate(IV) ion,
Sn(OH) 6
2– . This is the negative ion
present in crystalline ‘trihydrates’ of
the type K 2 Sn 2 O 3 .3H 2 O.
Tin(II) oxide gives the trihydroxostannate(II) ion in alkaline solutions
SnO(s) + OH
– (aq) + H 2 O(l) →
Sn(OH) 3
– (aq)
Stannate(IV) compounds were formerly referred to as orthostannates
(SnO 4
4– ) or metastannates (SnO 3
2– ).
Stannate(II) compounds were called
stannites.
stannic compounds Compounds
of tin in its higher (+4) oxidation
state; e.g. stannic chloride is tin(IV)
chloride.
501
stannic compounds
s
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staggered See conformation.
staggered conformation See conformation.
stainless steel A form of *steel
containing at least 11–12% of
chromium, a low percentage of carbon, and often some other elements,
notably nickel and molybdenum.
Stainless steel does not rust or stain
and therefore has a wide variety of
uses in industrial, chemical, and domestic environments. A particularly
successful alloy is the steel known as
18–8, which contains 18% Cr, 8% Ni,
and 0.08% C.
stalactites and stalagmites Accretions of calcium carbonate in
limestone caves. Stalactites are tapering cones or pendants that hang
down from the roofs of caves; stalagmites are upward projections from
the cave Ûoor and tend to be broader
at their bases than stalactites. Both
are formed from drips of water containing calcium hydrogencarbonate
in solution and may take thousands
of years to grow.
standard cell A *voltaic cell, such
as a *Clark cell, or *Weston cell,
used as a standard of e.m.f.
standard electrode An electrode
(a half cell) used in measuring electrode potential. See hydrogen half
cell.
standard electrode potential See
electrode potential.
standard solution A solution of
known concentration for use in volumetric analysis.
standard state A state of a system
used as a reference value in thermodynamic measurements. Standard
states involve a reference value of
pressure (usually one atmosphere,
101.325 kPa) or concentration (usually 1 M). Thermodynamic functions
are designated as ‘standard’ when
they refer to changes in which reactants and products are all in their
standard and their normal physical
state. For example, the standard
molar enthalpy of formation of water
at 298 K is the enthalpy change for
the reaction
H 2 (g) + ½O 2 (g) → H 2 O(l)
∆HŠ 298 = –285.83 kJ mol
–1
. Note the
superscript Š is used to denote standard state and the temperature
should be indicated.
standard temperature and pressure See s.t.p.
stannane See tin(iv) hydride.
stannate A compound formed by
reaction of tin oxides (or hydroxides)
with alkali. Tin oxides are amphoteric (weakly acidic) and react to give
stannate ions. Tin(IV) oxide with
molten alkali gives the stannate(IV)
ion
SnO 2 + 2OH
–
→ SnO 3
2– + H 2 O
In fact, there are various ions present
in which the tin is bound to hydroxide groups, the main one being the
hexahydroxostannate(IV) ion,
Sn(OH) 6
2– . This is the negative ion
present in crystalline ‘trihydrates’ of
the type K 2 Sn 2 O 3 .3H 2 O.
Tin(II) oxide gives the trihydroxostannate(II) ion in alkaline solutions
SnO(s) + OH
– (aq) + H 2 O(l) →
Sn(OH) 3
– (aq)
Stannate(IV) compounds were formerly referred to as orthostannates
(SnO 4
4– ) or metastannates (SnO 3
2– ).
Stannate(II) compounds were called
stannites.
stannic compounds Compounds
of tin in its higher (+4) oxidation
state; e.g. stannic chloride is tin(IV)
chloride.
501
stannic compounds
s
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