diff --git a/common/lib/capa/capa/chem/chemcalc.py b/common/lib/capa/capa/chem/chemcalc.py
index a58a3ac85d..389e688cf4 100644
--- a/common/lib/capa/capa/chem/chemcalc.py
+++ b/common/lib/capa/capa/chem/chemcalc.py
@@ -218,6 +218,9 @@ def render_to_html(eq):
             return u'\u2192'
         if arrow == '<->':
             return u'\u2194'
+
+        # this won't be reached unless we add more arrow types, but keep it to avoid explosions when
+        # that happens.
         return arrow
 
     def render_expression(ex):
@@ -391,36 +394,40 @@ def chemical_equations_equal(eq1, eq2, exact=False):
     chemical_equations_equal('H2 + O2 -> H2O2', '2 H2 + 2 O2 -> 2 H2O2', exact=True) -> False
 
 
-    If there's a syntax error, we raise pyparsing.ParseException.
+    If there's a syntax error, we return False.
     """
 
     left1, arrow1, right1 = split_on_arrow(eq1)
     left2, arrow2, right2 = split_on_arrow(eq2)
 
     if arrow1 == '' or arrow2 == '':
-        raise ParseException("Could not find arrow.  Legal arrows: {0}".format(ARROWS))
+        return False
 
     # TODO: may want to be able to give student helpful feedback about why things didn't work.
     if arrow1 != arrow2:
         # arrows don't match
         return False
 
-    factor_left = divide_chemical_expression(left1, left2)
-    if not factor_left:
-        # left sides don't match
-        return False
+    try:
+        factor_left = divide_chemical_expression(left1, left2)
+        if not factor_left:
+            # left sides don't match
+            return False
 
-    factor_right = divide_chemical_expression(right1, right2)
-    if not factor_right:
-        # right sides don't match
-        return False
+        factor_right = divide_chemical_expression(right1, right2)
+        if not factor_right:
+            # right sides don't match
+            return False
 
-    if factor_left != factor_right:
-        # factors don't match (molecule counts to add up)
-        return False
+        if factor_left != factor_right:
+            # factors don't match (molecule counts to add up)
+            return False
 
-    if exact and factor_left != 1:
-        # want an exact match.
-        return False
+        if exact and factor_left != 1:
+            # want an exact match.
+            return False
 
-    return True
+        return True
+    except ParseException:
+        # Don't want external users to have to deal with parsing exceptions.  Just return False.
+        return False
diff --git a/common/lib/capa/capa/chem/tests.py b/common/lib/capa/capa/chem/tests.py
index 9d415ad402..34d903ec1d 100644
--- a/common/lib/capa/capa/chem/tests.py
+++ b/common/lib/capa/capa/chem/tests.py
@@ -1,3 +1,4 @@
+import codecs
 from fractions import Fraction
 from pyparsing import ParseException
 import unittest
@@ -55,15 +56,17 @@ class Test_Compare_Equations(unittest.TestCase):
         self.assertTrue(chemical_equations_equal('H2 + O2 -> H2O2',
                                                  'O2 + H2 -> H2O2', exact=True))
 
-        
-    def test_syntax_errors(self):
-        self.assertRaises(ParseException, chemical_equations_equal,
-                          'H2 + O2 a-> H2O2',
-                          '2O2 + 2H2 -> 2H2O2')
 
-        self.assertRaises(ParseException, chemical_equations_equal,
-                          'H2 + O2 ==> H2O2',   # strange arrow
-                          '2O2 + 2H2 -> 2H2O2')
+    def test_syntax_errors(self):
+        self.assertFalse(chemical_equations_equal('H2 + O2 a-> H2O2',
+                                                  '2O2 + 2H2 -> 2H2O2'))
+
+        self.assertFalse(chemical_equations_equal('H2O( -> H2O2',
+                                                  'H2O -> H2O2'))
+
+
+        self.assertFalse(chemical_equations_equal('H2 + O2 ==> H2O2',   # strange arrow
+                                                  '2O2 + 2H2 -> 2H2O2'))
 
 
 class Test_Compare_Expressions(unittest.TestCase):
@@ -294,6 +297,29 @@ class Test_Render_Equations(unittest.TestCase):
         log(out + ' ------- ' + correct, 'html')
         self.assertEqual(out, correct)
 
+    def test_render_eq1(self):
+        s = "H^+ + OH^- -> H2O"
+        out = render_to_html(s)
+        correct = u'<span class="math">H<sup>+</sup>+OH<sup>-</sup>\u2192H<sub>2</sub>O</span>'
+        log(out + ' ------- ' + correct, 'html')
+        self.assertEqual(out, correct)
+
+    def test_render_eq2(self):
+        s = "H^+ + OH^- <-> H2O"
+        out = render_to_html(s)
+        correct = u'<span class="math">H<sup>+</sup>+OH<sup>-</sup>\u2194H<sub>2</sub>O</span>'
+        log(out + ' ------- ' + correct, 'html')
+        self.assertEqual(out, correct)
+
+        
+    def test_render_eq3(self):
+        s = "H^+ + OH^- <= H2O"   # unsupported arrow
+        out = render_to_html(s)
+        correct = u'<span class="math"><span class="inline-error inline">H^+ + OH^- <= H2O</span></span>'
+        log(out + ' ------- ' + correct, 'html')
+        self.assertEqual(out, correct)
+
+
 
 def suite():
 
@@ -305,6 +331,6 @@ def suite():
 
 if __name__ == "__main__":
     local_debug = True
-    with open('render.html', 'w') as f:
+    with codecs.open('render.html', 'w', encoding='utf-8') as f:
         unittest.TextTestRunner(verbosity=2).run(suite())
     # open render.html to look at rendered equations