Update gas mixture with correct n calculation

src/properties/test_helpers.rs

@@ -0,0 +1,45 @@
+use super::thermo_fit::{Phase, SpeciesElement, SpeciesThermoData, ThermoPolynomial};
+
+pub fn simple_thermo_polynomial(
+    cp_over_r: f64,
+    h_b: f64,
+    s_b: f64,
+    temp_range: (f64, f64),
+) -> ThermoPolynomial {
+    ThermoPolynomial {
+        a: vec![0.0, 0.0, cp_over_r, 0.0, 0.0, 0.0, 0.0, h_b, s_b],
+        temp_range,
+    }
+}
+
+pub fn h2_o2_h2o_thermo_data() -> Vec<SpeciesThermoData> {
+    vec![
+        SpeciesThermoData::new(
+            "H2",
+            vec![SpeciesElement { element: "H".to_string(), count: 2.0 }],
+            Phase::Gas,
+            vec![simple_thermo_polynomial(3.5, -1012.0, 29.11, (200.0, 6000.0))],
+            2.01594,
+            0.0,
+        ),
+        SpeciesThermoData::new(
+            "O2",
+            vec![SpeciesElement { element: "O".to_string(), count: 2.0 }],
+            Phase::Gas,
+            vec![simple_thermo_polynomial(3.5, -1005.0, 30.03, (200.0, 6000.0))],
+            31.9988,
+            0.0,
+        ),
+        SpeciesThermoData::new(
+            "H2O",
+            vec![
+                SpeciesElement { element: "H".to_string(), count: 2.0 },
+                SpeciesElement { element: "O".to_string(), count: 1.0 },
+            ],
+            Phase::Gas,
+            vec![simple_thermo_polynomial(4.0, -29192.0, 23.03, (200.0, 6000.0))],
+            18.01528,
+            -241826.0,
+        ),
+    ]
+}